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Standardized Calendar Time

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  • Klaus Schmid
    Hello all, I found some really useful informations here, many thanks to all contributing volunteers. Here is a small article related to the topic of this group
    Message 1 of 28 , Oct 3, 2004
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      Hello all,

      I found some really useful informations here,
      many thanks to all contributing volunteers.

      Here is a small article related to the topic of this group

      http://klaus.shyper.com/

      Comments welcome.

      -- Klaus
    • piebaldconsult
      ISO8601 doesn t deal with DST because it s not necessary, and messy, and just plain stupid. When sending time data, for instance when a conference call will
      Message 2 of 28 , Oct 6, 2004
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        ISO8601 doesn't deal with DST because it's not necessary, and messy,
        and just plain stupid. When sending time data, for instance when a
        conference call will take place, you just send it in UTC. The
        receiving party will adjust it for where they are.

        _You_ know the time zone and DST rules where _you_ are, _they_ know
        the rules where _they_ are. Neither of you needs to know the rules at
        the other's end, so why send it? Unless of course you're too lazy to
        do the adjustment yourself and want your partner to make _two_
        adjustments. Fortunately your computer will probably handle it anyway.

        Also, don't forget that DST doesn't necessarily work on hour
        increments.
      • Klaus Schmid
        Agree, to fix international events UTC is perfect. A time zone with DST rules together can be considered as a timescale. So if you change your location you may
        Message 3 of 28 , Oct 6, 2004
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          Agree, to fix international events UTC is perfect. A time zone with
          DST rules together can be considered as a timescale. So if you change
          your location you may set your default timescale to the timescale of
          your new location. Any calendar time can be converted from one
          timescale into another timescale, including UTC. If it is not clear
          by the context which timescale is the default, the timescale should
          be indicated together with the calendar time.
          I think this model is sound, only few details should be cared about,
          as discussed in my short article.

          Here another (invented) example for the timescale normalization:

          not normalized normalized UTC-offset
          -- -- (calendar minutes)
          2004-10-06T23:59_end 2004-10-06T23:59_end 137
          2004-10-07T00:00_begin 2004-10-06T24:00_begin 137
          ... ... 137
          2004-10-07T01:28_begin 2004-10-06T25:28_begin 137
          ... ... 137
          2004-10-07T02:43_end 2004-10-06T26:43_end 137
          2004-10-07T01:28_begin 2004-10-07T01:28_begin 61
          ... ... 61
          2004-10-07T02:43_end 2004-10-07T02:43_end 61


          -- Klaus
        • Tex Texin
          I agree with you that time zone and daylight savings are very difficult to work with and change in unpredictable ways at times. However, difficulty is not a
          Message 4 of 28 , Oct 7, 2004
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            I agree with you that time zone and daylight savings are very difficult to work
            with and change in unpredictable ways at times.
            However, difficulty is not a good argument for not supporting them.

            And although you are correct, that if you and I are discussing an event, we
            each know the offset to use to calculate our local time, there are many other
            situations, such as where you and I might be discussing meeting in a location
            separate from our current locations, and therefore not know the offset or the
            local rules for daylight savings etc.

            So, if I want to arrange to meet you in tibet at 5pm tibetan time, what value
            in UTC do I send to you to confirm the time?
            Since neither of us know without researching it, it seems clear that it can't
            simply be presumed that users "know" the necessary offsets.

            Mail headers also transmit time zone offsets btw.
            tex


            piebaldconsult wrote:
            >
            > ISO8601 doesn't deal with DST because it's not necessary, and messy,
            > and just plain stupid. When sending time data, for instance when a
            > conference call will take place, you just send it in UTC. The
            > receiving party will adjust it for where they are.
            >
            > _You_ know the time zone and DST rules where _you_ are, _they_ know
            > the rules where _they_ are. Neither of you needs to know the rules at
            > the other's end, so why send it? Unless of course you're too lazy to
            > do the adjustment yourself and want your partner to make _two_
            > adjustments. Fortunately your computer will probably handle it anyway.
            >
            > Also, don't forget that DST doesn't necessarily work on hour
            > increments.
          • piebaldconsult
            No, giving some arbitrary DST thingy is no good, it can still be misinterpreted. A UTC value with _one_ offset is much clearer. If you _must_ give a value in
            Message 5 of 28 , Oct 8, 2004
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              No, giving some arbitrary DST thingy is no good, it can still be
              misinterpreted. A UTC value with _one_ offset is much clearer. If you
              _must_ give a value in some local time, simply include the offset. If
              you don't know the offset, then don't try to give a local time.
              Giving _two_ offsets (as in "2004/10/08T15:00-08:00+01:00") is silly,
              just combine them into one.

              DST is evil and hopefully will be abolished some day. If I ran a
              company I would not use it.

              I now live in Arizona, where _most_ of the state does not use DST,
              but I understand that _some_ of the local Indian reservations do.
              Just how would you set up a series of meetings with the local mayors
              and tribal chiefs if you were interviewing each in his or her office?
              Would _you_ understand if they said they were in "Mountain Zuni
              Daylight Time"? Or "Mountain Navajo Standard Time"? But you _would_
              understand if they said, "Meet me in my office at 2004/10/08T15:00-
              06:00". You _don't_ care what's involved in that -06:00, you just
              need to show up on time. (By the way, I don't know which nations use
              what offset.)

              In the example someone gave about meeting in some third location
              where neither party knows the correct offset, I don't know what you'd
              do. If the offset isn't known, you can't give an offset, and knowing
              some obscure disignation like "PST" won't help if it's not known what
              it means. You _must_ know the offset to give a local time, simply
              adding "PST" to the end doesn't help, and may be misinterpreted by
              the different parties. Once the offset is known, use it. Why
              say "PST" when you know it equates to "-07:00"? Just say "-07:00" and
              be clear!
            • Klaus Schmid
              Does it make any difference if we say 2004-10-08T15:00-06:00 or if we say 2004-10-08T21:00Z? I could think of two points: a) The first notation is easier and
              Message 6 of 28 , Oct 10, 2004
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                Does it make any difference if we say 2004-10-08T15:00-06:00 or
                if we say 2004-10-08T21:00Z? I could think of two points:

                a) The first notation is easier and faster: only the UTC offset
                which applies to the indicated time has to be found out. Otherwise
                some math is required and eventually some effort to find out the
                number of calendar days of the month into which the time is shifted.

                b) The first notation contains some additional information, which
                might be interesting for the receiver: the difference to UTC may
                serve as a rough indication of the location of the sender. Further,
                the receiver may assume that the wall clock of the sender has the
                same difference to UTC.

                At least if we cannot exclude a DST rule on the sender side, this
                additional information is only vague and related only to a single
                point in time.

                Referring your example, I would certainly prefer to know the
                difference to UTC indicated according ISO8601. I agree with you
                about textual time zone designations and abbreviations, the numeric
                representation seems way superior.

                If I would live in Arizona and someone of the Navajo community would
                invite me, yes, I could ask for the offset on which the indicated
                time by him or her is based on. Assuming a heavy storm comes up and
                we are not able to visit a certain site as originally planned, he or
                she could invite me again for "next week, same place and same time".
                Unfortunatly in the meantime a DST period starts in the Navajo
                Nation and since I was not aware of the last DST transition, I would
                be just one hour too late.

                So can we ignore DST and only care about the offset? Theoretically
                yes, but in some situations it seems to be more practical if we know
                about the DST of the sender. And normally this information is
                present so why should we hide or ignore it?

                As an example the request for DST information may look like:
                Q.: Could you inform me about your DST rules?
                A.: Our DST rules in Navajo Nations are the same as in other places
                in the United States.
                Since I am not familiar with these rules I would then probably try
                to research the details by my own.

                How it _could_ look like:
                I ask for the default timescale of Navajo Nations.
                Clear answer: US17
                I use the default timescale of Arizona which is: C17

                Now I know that our timescales are identical in winter but not in
                summer. In detail, "17" indicates offset in winter, "US" indicates a
                well defined DST rule and "C" indicates a constant offset without
                any DST rules. In deeper detail, the difference to UTC would be 17-
                24 = -7 calendar hours, although knowledge of this detail would not
                be needed here.

                Provided I am sure to be in the DST period or outside the same and I
                know that US17 within the DST period is identical to C18, I could
                easily handle my appointments off the top of my head.

                In my electronic time scheduler I would input:
                Visit in Navajo Nations: 2004-10-08T15:00 US17
                And it would show me:
                Visit in Navajo Nations: 2004-10-08T14:00 C17 (defined as 2004-10-
                08T15:00 US17)

                In time periods of about one week my operation system would update
                automatically the definitions of all needed timescales from a remote
                server, including any changes of DST rules as well as upcoming
                changes of the UTC timescale due to leapseconds.

                This would not solve _all_ problems related to DST and therefor
                should _not_ stimulate communities, namely politicans, to change
                their DST rules at any time by their will. But I think it would
                solve _some_ problems related to timescales in general, not
                necessarily only those affected by DST.

                Thanks for your comments.

                -- Klaus
              • johnmsteele
                On your first point, the standard allows either notation. I agree with your point about the usefulness of knowing the sender s time zone. That usefulness
                Message 7 of 28 , Oct 13, 2004
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                  On your first point, the standard allows either notation. I agree
                  with your point about the usefulness of knowing the sender's time
                  zone. That usefulness remains even if there is the possibility of a
                  one hour DST ambiguity at certain times of year, as I have a general
                  sense of local business hours in UTC time. ISO8601 simply says
                  if "local" time is used, the offset MUST be given. ISO8601 does not
                  attempt to control local offset based on longitude, it simply assumes
                  local time is determined by civil authority and the offset to UTC can
                  be determined, so that the time given is resolvable to UTC by
                  mechanized computation, with no reference to context.

                  Your second question is more complex and may be beyond ISO8601. Some
                  people have an "international" orientation, whether they deal in
                  international telephone calls, business or personal travel, etc, and
                  understand time zones well. Others have much more of a "local"
                  orientation and we certainly have people in the US who get confused
                  when they go from Eastern to Central time zones. We set up another
                  group, WWDATES, to deal with these issues; unfortunately no one seems
                  to address them there. There is simply a portion of the population
                  that will never shift from provincial timestyles to 8601. But I think
                  that is the place to discuss simple changes to those local styles
                  that can allow clearer transformation.

                  "Same time, next week" is obviously not 8601 compliant. It involves
                  human computation and context interpretation to determine what is
                  meant. The whole issue of when countries change between standard and
                  daylight ("summer" time to Europeans) time is outside the scope of
                  8601.

                  I really question whether you need to check these differences every
                  week. For North America(*), Europe, Australia, Russia and former
                  republics, the rules are well defined by law. A few countries either
                  base them on a non-Gregorian calendar (Iraq) or determine them by law
                  each year (Israel and Brazil). Leap seconds are declared months in
                  advance by IERS and incorporated in the last second of June and
                  December. There was a thread some time ago (search archives) about
                  DST schedules and how often changes occur.

                  (*)NOTE: Your "US" rule should probably be "North American" as Canada
                  and Mexico use the same switching date as the US, they also allow
                  discretion by Canadian province or Mexican state as to whether to
                  observe DST. I believe two Canadian provinces are exceptions that use
                  a different local time, but correct date for the transition.

                  I find your positive notation for negative offsets from UTC very
                  confusing. For me +17 != -7. They are equal if you ignore 24 hour
                  overflow, but in a "time scale" such overflow rolls into the date.
                  The range of offsets from UTC is clearly plus and minus 12 hours, and
                  using those offsets results in clear date computation as well as
                  time. Trying to call the range 0-24 hours results in either a lot of
                  specialized arithmetic or date errors.
                  NOTE: UTC isn't a "real" timescale due to leapseconds, and local time
                  is less of a time scale due to legislative time zone changes and DST.




                  --- In ISO8601@yahoogroups.com, "Klaus Schmid" <klaus.schmid@w...>
                  wrote:
                  >
                  > Does it make any difference if we say 2004-10-08T15:00-06:00 or
                  > if we say 2004-10-08T21:00Z? I could think of two points:
                  >
                  > > If I would live in Arizona and someone of the Navajo community
                  would
                  > invite me, yes, I could ask for the offset on which the indicated
                  > time by him or her is based on. Assuming a heavy storm comes up and
                  > we are not able to visit a certain site as originally planned, he
                  or
                  > she could invite me again for "next week, same place and same time".
                  >
                • Klaus Schmid
                  The notation of EU25 instead of EU+01 and US18 instead of US-06 should actually avoid the confusion caused by signed numbers. EU25 and US18 are _names_. Names
                  Message 8 of 28 , Oct 19, 2004
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                    The notation of EU25 instead of EU+01 and US18 instead of US-06
                    should actually avoid the confusion caused by signed numbers. EU25
                    and US18 are _names_. Names according this scheme contain
                    information about the minimum UTC-offset. The idea about "EU"
                    and "US" is to reflect the authority which defines the DST rules.
                    Other countries may adopt the DST rules and may use e.g. US25. There
                    are two mappings: 1) Mapping from country, region, city or person to
                    timescale. 2) Mapping from timescale to minimum UTC-offset and DST-
                    rules. Referring the first mapping a timescale is similar to a
                    prefix phone-number of a country or city and can be included in the
                    personal contact data accordingly. The second mapping allows finally
                    the conversion of a calendar time from one timescale into any other
                    timescale.

                    I am not sure about your last note. For me "UTC-time" as any "local
                    time" are calendar timescales based on TAI (atomic timescale).
                    Calendar timescales need conventions.

                    Thank you for your comments.

                    -- Klaus
                  • John Steele
                    I was not aware of the EU25 notation or the two step mapping to actual offset. I still find it overly cumbersome and prefer just stating an offset to UTC. I
                    Message 9 of 28 , Oct 19, 2004
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                      I was not aware of the EU25 notation or the two step mapping to actual offset. I still find it overly cumbersome and prefer just stating an offset to UTC. I suppose you are correct regarding US vs NA for our DST rule. We did not consult Mexico or Canada in passing our law; they simply chose to adopt it, and any of the three could change independently, although calling it the North American DST rule might help prevent that :)
                       
                      I wish the EU and the US could agree on dates for DST changes (we are a week apart in the spring). It would be nice to have a fixed date rule for everyone in the Northern hemisphere who observes DST, and another one for the Southern.  The EU idea of all zones changing at a given UTC time works OK for a few time zones but not worldwide. Russia, which has many time zones, changes at a given local time in each zone, like the US, but uses EU dates.
                       
                      A timescale must be monotonic, continuous, and isotonic (equal interval). Civil times with DST rules and leap seconds are clearly not monotonic and continuous. UTC presently uses TAI tics, correcting with leap seconds to match the rotation of the earth. In the past, the UTC tic rate was offset deliberately and variably from TAI to match earth rotation. Strictly speaking, none can be considered a true timescale as they violate one or more requirements. Over human lifetimes, the violations are small, declared, and documented, and these time systems are used as approximate time scales. In certain areas, notably astronomy, using them as time scales creates problems, as the interval between timestamps can not be determined accurately as in TAI.  Since 1972, UTC could be used as a time scale if and only if a cumulative leap second table is consulted and used to correct time interval, as the offset to TAI has changed by 22 seconds over that time frame. (granted, few disciplines need such exact interval)

                      Klaus Schmid <klaus.schmid@...> wrote:


                      The notation of EU25 instead of EU+01 and US18 instead of US-06
                      should actually avoid the confusion caused by signed numbers. EU25
                      and US18 are _names_. . . .

                      I am not sure about your last note. For me "UTC-time" as any "local
                      time" are calendar timescales based on TAI (atomic timescale).
                      Calendar timescales need conventions.

                      Thank you for your comments.

                      -- Klaus

                    • piebaldconsult
                      DST should be abolished. It was never a good idea.
                      Message 10 of 28 , Oct 20, 2004
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                        DST should be abolished. It was never a good idea.
                      • John Steele
                        I certainly accept that it is a PITA for those involved in precise timekeeping. As a civilian, I like the long evenings in the summer, and feel it better
                        Message 11 of 28 , Oct 20, 2004
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                          I certainly accept that it is a PITA for those involved in precise timekeeping. As a "civilian," I like the long evenings in the summer, and feel it better balances the hours of daylight to the hours people keep. At more southerly latitudes, the length of day doesn't very so much, and it may be more nuisance than benefit (I guess with worldwide perspective, I should say more equator-ward latitudes).
                           
                          So, I don't agree it should be abolished. I do think it could be improved.  I think countries should have option of using ir not using, but if they use, better worldwide agreement on the dates for switching (probably two rules for the two hemispheres), and more consistency on the exact time of switching. Since the UN can't agree on anything really important, like peace, genocide, etc, maybe it could argue this to death.

                          piebaldconsult <PIEBALDconsult@...> wrote:

                          DST should be abolished. It was never a good idea.
                        • Vincent Lefevre
                          On 2004-10-20 06:55:40 -0700, John Steele wrote: [Abolishing DST] ... Instead of changing the clock, you could change opening/closing hours and things like
                          Message 12 of 28 , Oct 20, 2004
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                            On 2004-10-20 06:55:40 -0700, John Steele wrote:
                            [Abolishing DST]
                            > I certainly accept that it is a PITA for those involved in precise
                            > timekeeping. As a "civilian," I like the long evenings in the
                            > summer, and feel it better balances the hours of daylight to the
                            > hours people keep. At more southerly latitudes, the length of day
                            > doesn't very so much, and it may be more nuisance than benefit (I
                            > guess with worldwide perspective, I should say more equator-ward
                            > latitudes).

                            Instead of changing the clock, you could change opening/closing hours
                            and things like that (this would be more flexible). Reducing the
                            number of timezones would also be a good thing (like in Europe,
                            where most countries use CET).

                            --
                            Vincent Lefèvre <vincent@...> - Web: <http://www.vinc17.org/>
                            100% accessible validated (X)HTML - Blog: <http://www.vinc17.org/blog/>
                            Work: CR INRIA - computer arithmetic / SPACES project at LORIA
                          • volsano@aol.com
                            ... And double-ditto for time zones. A stupid idea, invented by the railway companies for their own convenience, and should have been dumped along with the
                            Message 13 of 28 , Oct 20, 2004
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                              > DST should be abolished. It was never a good idea.

                              And double-ditto for time zones. A stupid idea, invented by the railway
                              companies for their own convenience, and should have been dumped along with the
                              steam locomotive.

                              Every locality should be free to set their own local time rather than be
                              dictated to by defunct commercial companies.

                              Provided all localities also publish their UTC offset, computers can do the
                              translations, and no one need ever get confused.

                              :-/
                              VS
                            • piebaldconsult
                              ... hours Exactly, don t make _me_ change _my_ clock, just because _you_ like evening hours. If _you_ want to run _your_ business with different hours in the
                              Message 14 of 28 , Oct 21, 2004
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                                > Instead of changing the clock, you could change opening/closing
                                hours

                                Exactly, don't make _me_ change _my_ clock, just because _you_ like
                                evening hours. If _you_ want to run _your_ business with different
                                hours in the summer then do so, but leave _me_ alone.

                                Time zones weren't invented by the railroads. Time zones were
                                developed by the guv'mint, because the advent of the railroads
                                demonstrated that we need a standard way of saying what time it is in
                                various places.

                                As to abolishing time zones, I'm not so sure, yes it can be done more
                                accurately now, with computers. And if I use an offset of "-7:12" I
                                can send a message to someone with an offset of "-7:33", I send in
                                UTC, he receives and knows when to meet or whatever. But if I simply
                                call him on the phone and tell him, I would need to know the UTC.
                                That gets us into simply using UTC (which some favor anyway) and not
                                using local time. I don't know where I'm going with this, so I'll
                                stop.

                                What I don't like is that the time zones are political, zigging and
                                zagging around state boundaries and such. I think they should be in
                                smaller increments, like ten minutes or so, and rigidly aligned along
                                latitude lines.

                                It ocurred to me that we have clocks that pull in the signal from the
                                time clock, why not have some that use GPS to know where they are too?
                              • volsano@aol.com
                                ... My source of or information (or possibly misinformation) was wikipedia: The first time zone in the world was established by British railroads December 1,
                                Message 15 of 28 , Oct 21, 2004
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                                  > Time zones weren't invented by the railroads.

                                  My source of or information (or possibly misinformation) was wikipedia:

                                  "The first time zone in the world was established by British railroads
                                  December 1, 1847"
                                  http://en.wikipedia.org/wiki/Time_Zones

                                  If the article is wrong about that, you could update it for them.

                                  But either way, my point was the time zones are a steam-driven invention to
                                  serve the perceived needs of the 19th Century.

                                  I've seen almost zero justification for why we need them today.

                                  And even less for the use of the marketing moniker UTC. Universal? Really?
                                  How do I show a zonal offset for the local time of day at the location of NASA's
                                  Mars Exploration Rover, Spirit?

                                  :-/
                                  VS
                                • Harry Shipley
                                  It depends on what you mean by a time zone. The railways, I believe, created a time standard of Greenwich meridian time applying throughout their systems,
                                  Message 16 of 28 , Oct 22, 2004
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                                    It depends on what you mean by a time zone. The railways, I believe,
                                    created a time standard of Greenwich meridian time applying throughout their
                                    systems, instead of the local solar times that had up till then been used.
                                    But until someone came up with another "zone" - taking its time from another
                                    meridian, then there was only one zone and everyone *could* have adopted it.

                                    Harry Shipley

                                    -----Original Message-----
                                    From: volsano@... [mailto:volsano@...]
                                    Sent: 21 October 2004 15:27
                                    To: ISO8601@yahoogroups.com
                                    Subject: Re: [ISO8601] Re: Standardized Calendar Time


                                    > Time zones weren't invented by the railroads.

                                    My source of or information (or possibly misinformation) was wikipedia:

                                    "The first time zone in the world was established by British railroads
                                    December 1, 1847"
                                    http://en.wikipedia.org/wiki/Time_Zones



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                                  • johnmsteele
                                    ... in ... The US Naval Observatory seems pretty convinced that time zones were introduced by the railroads in 1883 and not mandated by the government until
                                    Message 17 of 28 , Oct 23, 2004
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                                      --- In ISO8601@yahoogroups.com, "piebaldconsult"
                                      <PIEBALDconsult@a...> wrote:
                                      > Time zones weren't invented by the railroads. Time zones were
                                      > developed by the guv'mint, because the advent of the railroads
                                      > demonstrated that we need a standard way of saying what time it is
                                      in
                                      > various places.
                                      >
                                      The US Naval Observatory seems pretty convinced that time zones were
                                      introduced by the railroads in 1883 and not mandated by the
                                      government until 1918.
                                      http://aa.usno.navy.mil/faq/docs/us_tzones.html
                                      "History of Standard Time in the U.S.
                                      Standard time in time zones was instituted in the U.S. and Canada by
                                      the railroads on 18 November 1883. Before then, time of day was a
                                      local matter, and most cities and towns used some form of local solar
                                      time, maintained by some well-known clock (for example, on a church
                                      steeple or in a jeweler's window). The new standard time system was
                                      not immediately embraced by all, however.

                                      Use of standard time gradually increased because of its obvious
                                      practical advantages for communication and travel. Standard time in
                                      time zones was not established in U.S. law until the Act of March 19,
                                      1918, sometimes called the Standard Time Act. The act also
                                      established daylight saving time, itself a contentious idea. Daylight
                                      saving time was repealed in 1919, but standard time in time zones
                                      remained in law, with the Interstate Commerce Commission (ICC) having
                                      the authority over time zone boundaries. Daylight time became a local
                                      matter. It was re-established nationally early in World War II, and
                                      was continuously observed until the end of the war. After the war its
                                      use varied among states and localities. The Uniform Time Act of 1966
                                      provided standardization in the dates of beginning and end of
                                      daylight time in the U.S. but allowed for local exemptions from its
                                      observance. The act also continued the authority of the ICC over time
                                      zone boundaries. In subsequent years, Congress transferred the
                                      authority over time zones to the U.S. Department of Transportation
                                      (DOT), modifed (several times) the beginning date of daylight time,
                                      and renamed the three westernmost time zones. . . ."

                                      The role of the railroad may have been replaced by other common
                                      carriers, but I think airline schedules, tv schedules and many other
                                      things that affect most of us are much better expressed in zone time
                                      that local apparent time. Whether UTC would work (one worldwide time
                                      zone) is probably another debate, but a return to every location
                                      having its own local time would be crazy. (At the moment, US law
                                      requires common carriers to use local time zone based schedules, so
                                      if you want change, start with Congress. Other countries mandate
                                      their time zones too.)
                                    • Fred Bone
                                      ... The USNO, of course, is unaware of the existence of countries outside the US. Or their governments, apparently. Not that any of this has anything to do
                                      Message 18 of 28 , Oct 24, 2004
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                                        johnmsteele said:

                                        > --- In ISO8601@yahoogroups.com, "piebaldconsult"
                                        > <PIEBALDconsult@a...> wrote:
                                        > > Time zones weren't invented by the railroads. Time zones were
                                        > > developed by the guv'mint, because the advent of the railroads
                                        > > demonstrated that we need a standard way of saying what time it is
                                        > in
                                        > > various places.
                                        > >
                                        > The US Naval Observatory seems pretty convinced that time zones were
                                        > introduced by the railroads in 1883 and not mandated by the
                                        > government until 1918.
                                        >

                                        The USNO, of course, is unaware of the existence of countries outside the
                                        US. Or their governments, apparently.

                                        Not that any of this has anything to do with ISO8601, which needs to deal
                                        with how things are, not how they were or ought to be. As long as parts
                                        of the world run their clocks on anything other than UTC, there will be a
                                        need to state the offset whenever you state a time-of-day, if you want to
                                        be unambiguous.
                                      • Klaus Schmid
                                        ... Which notation would children learn easier? E.g. if they had to convert calendar times 20:00 US18 into timescale EU25 resp. 20:00 US-06 into timescale
                                        Message 19 of 28 , Oct 24, 2004
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                                          johnmsteele wrote:
                                          > ...
                                          > I still find it overly cumbersome and prefer just stating an
                                          > offset to UTC.
                                          > ...

                                          Which notation would children learn easier?
                                          E.g. if they had to convert calendar times

                                          20:00 US18 into timescale EU25
                                          resp.
                                          20:00 US-06 into timescale EU+01

                                          According my experience children start with numbers from 0 to 100,
                                          adding and deducting. Negative numbers are learned some years later.

                                          Further on, imagine the time zone range of -12 to +12 would be
                                          traditionally numbered from 12 to 36, what would anyone prefer?

                                          Thanks for your comments.

                                          -- Klaus
                                        • johnmsteele
                                          ... outside the ... Apparently, so is this UK site. They credit the chief engineer of a Canadian railroad with proposing the system in 1878, adoption by US
                                          Message 20 of 28 , Oct 24, 2004
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                                            --- In ISO8601@yahoogroups.com, "Fred Bone" <fred.bone@d...> wrote:

                                            > The USNO, of course, is unaware of the existence of countries
                                            outside the
                                            > US. Or their governments, apparently.
                                            >

                                            Apparently, so is this UK site. They credit the chief engineer of a
                                            Canadian railroad with proposing the system in 1878, adoption by US
                                            railroads in 1883, and by other parts of the world in 1884, based on
                                            a conference held in the US. If they are wrong, please free to offer
                                            an alternate history.
                                            http://wwp.greenwichmeantime.com/info/time-zones-history.htm
                                            Standard Time
                                            The History of Time Zones
                                            Standard time the time of a town, region or country that is
                                            established by law or general usage as civil time. It is determined
                                            locally. The whole of China, one of the largest countries in the
                                            world, has decided to adopt a single time zone

                                            The concept of standard time was adopted in the late 19th century in
                                            an attempt to end the confusion that was caused by each community's
                                            use of its own solar time. Some such standard became increasingly
                                            necessary with the development of rapid railway systems and the
                                            consequent confusion of schedules that used scores of different local
                                            times kept in separate communities. (Local time varies continuously
                                            with change in longitude.)

                                            The need for a standard time was felt most particularly in the United
                                            States and Canada, where several extensive railway routes passed
                                            through places that differed by several hours in local time.

                                            Sir Sandford Fleming, a Canadian railway planner and engineer,
                                            outlined a plan for worldwide standard time in the late 1870s.
                                            Following this initiative, in 1884 delegates from 27 nations met in
                                            Washington, D.C., for the Meridian Conference and agreed on a system
                                            basically the same as that now in use.

                                            The present system employs 24 standard meridians of longitude (lines
                                            running from the North Pole to the South, at right angles to the
                                            Equator) 15º apart, starting with the prime meridian through
                                            Greenwich, England. These meridians are theoretically the centres of
                                            24 standard time zones; in practice, the zones have in many cases
                                            been subdivided or altered in shape for the convenience of
                                            inhabitants.

                                            Time is the same throughout each zone and differs from the
                                            international basis of legal and scientific time, Greenwich Mean Time
                                            (GMT) or Coordinated Universal Time (UTC), by an integral number of
                                            hours; minutes and seconds are the same.

                                            In a few regions, however, the legal time kept is not that of one of
                                            the 24 standard time zones because half-hour or quarter-hour
                                            differences are in effect there.

                                            Links
                                            Sir Sandford Fleming: website
                                            Sir Sandford Fleming: website

                                            The second link says this about Fleming:
                                            http://www.geo.ed.ac.uk/scotgaz/people/famousfirst28.html
                                            Sir Sandford Fleming
                                            1827 - 1915

                                            Canadian railway engineer, born in Kirkcaldy. He surveyed many of the
                                            major Canadian railway routes and became Chief Engineer of the
                                            Canadian Pacific Railway in 1872. In 1884, he devised a system of
                                            standard time, in which the world was divided into zones, which is
                                            now internationally recognised.

                                            He was knighted in 1897 and his name is remembered in the Sir
                                            Sandford Fleming College in Ontario, Canada.
                                          • Tex Texin
                                            Hi all, Where are we going? Been away for a few weeks and trying to sort thru the mail... Let me see if I got this straight. DST should be abolished. No, it
                                            Message 21 of 28 , Oct 24, 2004
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                                              Hi all,

                                              Where are we going? Been away for a few weeks and trying to sort thru the
                                              mail...

                                              Let me see if I got this straight. DST should be abolished. No, it should be
                                              more granular down to 10 minute gradations. We should eliminate negative
                                              offsets in time zone names to make it easier for children.
                                              And then some historical controversy over where zones came from.

                                              Here's my 2 cents.
                                              a) I am fine with abolishing daylight savings. However, the idea that
                                              individual businesses will change their hours when they see fit to maximize
                                              daylight, or energy usage, etc. is fairly broken, speaking as a consumer. I
                                              like my shopping opportunities to be predictable and consistent. I can tolerate
                                              some small number of changes and inconveniences but I would really not like a
                                              world where throughout sept. and oct. stores changed their hours and then again
                                              in march/april in unpredictable ways.

                                              b) I would not be fine with more zones and granularity. This takes an already
                                              hard problem and makes it harder.

                                              c) I don't think children have much use for time zones or any more use than
                                              adults, and so there isn't much of a problem being fixed here. It's not clear
                                              that it is much of an improvement. Without a significant motive or benefit, I
                                              am inclined to leave it as is.

                                              d) Which issues are relevant to 8601?
                                            • piebaldconsult
                                              ... Who are you to say my kid won t understand time zones and negative numbers? I remember understanding negative numbers in first grade because I have older
                                              Message 22 of 28 , Oct 25, 2004
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                                                > Which notation would children learn easier?
                                                > E.g. if they had to convert calendar times
                                                >
                                                > 20:00 US18 into timescale EU25
                                                > resp.
                                                > 20:00 US-06 into timescale EU+01
                                                >
                                                > According my experience children start with numbers from 0 to 100,
                                                > adding and deducting. Negative numbers are learned some years later.
                                                >

                                                Who are you to say my kid won't understand time zones and negative
                                                numbers? I remember understanding negative numbers in first grade
                                                because I have older siblings who were learning it, but the teacher
                                                said. "No no, you can't subtract three from two." It was very
                                                frustrating because I knew darn well that I could.

                                                Now my kid's grandparents are on opposite coasts, and we're in
                                                between, you can bet he'll know about time zones, even if we have to
                                                put up more clocks on the wall, with signs saying "Granddad"
                                                and "Grammie and Papa".

                                                Regardless, your proposal is ridiculous, the use of negative numbers
                                                is just fine, what might have made more sense from the beginning is
                                                if GMT had been made zone 12 rather than zone 0. But it didn't, so
                                                just deal with it.
                                              • Tex Texin
                                                Hi, I am not sure why you need to be so caustic in your answers. Of course, there is always some age before which a child does not know negative numbers. Maybe
                                                Message 23 of 28 , Oct 25, 2004
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                                                  Hi,

                                                  I am not sure why you need to be so caustic in your answers.

                                                  Of course, there is always some age before which a child does not know negative
                                                  numbers.

                                                  Maybe yours are past that, but that doesn't mean there isn't a benefit to
                                                  having an approach that makes it accessible to a wider audience. Actually,
                                                  there are quite a few adults that do not understand negative numbers...

                                                  That said, I don't think solving only that problem warrants the work that
                                                  changing the system would entail, so I wouldn't endorse the change myself.

                                                  Also, as this list is about ISO 8601 and since we don't seem to be discussing a
                                                  change to 8601, perhaps we should just agree this is off topic for this list.
                                                  (Should move to the worldwide user friendly dates list:
                                                  wwdates@yahoogroups.com.)

                                                  tex

                                                  piebaldconsult wrote:
                                                  >
                                                  > > Which notation would children learn easier?
                                                  > > E.g. if they had to convert calendar times
                                                  > >
                                                  > > 20:00 US18 into timescale EU25
                                                  > > resp.
                                                  > > 20:00 US-06 into timescale EU+01
                                                  > >
                                                  > > According my experience children start with numbers from 0 to 100,
                                                  > > adding and deducting. Negative numbers are learned some years later.
                                                  > >
                                                  >
                                                  > Who are you to say my kid won't understand time zones and negative
                                                  > numbers? I remember understanding negative numbers in first grade
                                                  > because I have older siblings who were learning it, but the teacher
                                                  > said. "No no, you can't subtract three from two." It was very
                                                  > frustrating because I knew darn well that I could.
                                                  >
                                                  > Now my kid's grandparents are on opposite coasts, and we're in
                                                  > between, you can bet he'll know about time zones, even if we have to
                                                  > put up more clocks on the wall, with signs saying "Granddad"
                                                  > and "Grammie and Papa".
                                                  >
                                                  > Regardless, your proposal is ridiculous, the use of negative numbers
                                                  > is just fine, what might have made more sense from the beginning is
                                                  > if GMT had been made zo ne12ratherthanzone0.Butitdidn't,so
                                                  > just deal with it.
                                                • g1smd_amsat_org
                                                  [2004-11-02] ... There is a handy list over at: http://timeanddate.com/time/dst2004b.html ... Even worse is arranging say a conference call between several
                                                  Message 24 of 28 , Nov 2, 2004
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                                                    [2004-11-02]



                                                    On 2004-Oct-06 piebaldconsult wrote:

                                                    > _You_ know the time zone and DST rules where _you_ are, _they_ know
                                                    > the rules where _they_ are. Neither of you needs to know the rules at
                                                    > the other's end, so why send it? Unless of course you're too lazy to
                                                    > do the adjustment yourself and want your partner to make _two_
                                                    > adjustments. Fortunately your computer will probably handle it anyway.

                                                    > Also, don't forget that DST doesn't necessarily work on hour
                                                    > increments.


                                                    On 2004-Oct-07 Tex Texin wrote:

                                                    > I agree with you that time zone and daylight savings are very
                                                    > difficult to work with and change in unpredictable ways at times.

                                                    There is a handy list over at: http://timeanddate.com/time/dst2004b.html


                                                    > ... there are many other situations, such as where you and I
                                                    > might be discussing meeting in a location separate from our
                                                    > current locations, and therefore not know the offset or the
                                                    > local rules for daylight savings etc.

                                                    Even worse is arranging say a conference call between several offices
                                                    in the US,
                                                    UK, Hong Kong and Japan.

                                                    All have offices that are open from 9am to 5pm in their local time.

                                                    The only way to be sure that everyone arrives at the same time is to
                                                    talk in UTC.

                                                    There are hundreds of places on the net where you can find the
                                                    date/time in UTC to a fraction of a second, any time of the day or night.


                                                    Assume it is the Northern Hemisphere Summer:

                                                    The US West Coast Office 9am-5pm (UTC-0700) is open 16:00-24:00 UTC
                                                    The US East Coast Office 9am-5pm (UTC-0400) is open 13:00-21:00 UTC
                                                    The UK Office is open 9am-5pm (UTC+0100) which is 08:00-16:00 UTC
                                                    The Hong Kong office 9am-5pm (UTC+0800) opens 01:00-09:00 UTC.
                                                    The Japanese Office 9am-5pm (UTC+0900) opens 00:00-08:00 UTC.

                                                    There is no time when all are open at the same time.

                                                    It looks best to schedule this as two: one at 08:00 for the UK and
                                                    Asia and another at 16:00 for US and UK, or: have it at around
                                                    Midnight UK time, with one person paid serious overtime there, while
                                                    it is late in the working day for the US (little bit of overtime for
                                                    East Coast US) and very first thing in the morning for the Asian end.

                                                    Trying to reconcile this without a list of UTC times would be a nightmare.




                                                    On 2004-Oct-08 piebaldconsult wrote:

                                                    > No, giving some arbitrary DST thingy is no good, it can still be
                                                    misinterpreted.

                                                    Another thought. I talk to someone in Australia once per week, and
                                                    they always tell me that they will call on Thursday at 09:00 UK Time.
                                                    In the Summer that is the same as 08:00 UTC of course.

                                                    As Summer has just ended, we have just put our clocks back by one
                                                    hour, so this week the call is expected at 09:00UTC as it happens.
                                                    From their end, they used to call at 17:00 in their local Winter Time
                                                    (UTC+0900), but they have just changed their local time up to UTC+1000
                                                    for their Summer Time.

                                                    If they call me at 17:00 in their local time now, then that is 07:00
                                                    in MY local time, and I'll not be best pleased. To get me at 09:00 in
                                                    MY local time, they will now need to call at 19:00 in their local
                                                    time; that's a shift of TWO hours (check it out, it is correct). That
                                                    is not obvious to many people.

                                                    I get the feeling that they would have added or subtracted just one
                                                    hour from their local time, making the call arrive at 06:00 or 08:00
                                                    in UK local time; and 06:00 is going to be even less well received.

                                                    An arrangement for 09:00 UTC all year round would be a lot easier, and
                                                    independant of all DST changes.


                                                    Yet another thought. If they said they would call me at 09:00+0100 and
                                                    now my local time zone has changed to be +0000, can I really assume
                                                    that they will call at what will be 08:00 for me? I would expect that
                                                    to be so, but can I be sure that they really saw their error in
                                                    stating MY zone, and they really meant 09:00 and got the zone wrong?


                                                    > DST is evil and hopefully will be abolished some day. If I ran a
                                                    company I would not use it.

                                                    DST is a necessary evil of you live more than 45 degrees from the Equator.

                                                    Without it, Summer daylight hours would be from 4 am to 8pm; we make
                                                    use of this by changing that to 5am to 9pm to make a longer evening.

                                                    However, we can't stay artificially ahead all year round, otherwise in
                                                    the Winter the most Northern places would have daylight from 9am to
                                                    5pm. In Northern Scotland it wouldn't be light until after 10am.

                                                    The mornings would be far too dark, so they change it back to be 8am
                                                    to 4pm equally spaced around the true astronomical midday.


                                                    > By the way, I don't know which nations use what offset.

                                                    Handy List: http://timeanddate.com/time/dst2004b.html

                                                    Even the 2005-Spring data is not yet available, and some change again
                                                    in only 4 months from now.




                                                    On 2004-Oct-13 piebaldconsult wrote:

                                                    > I think sending time values in UTC is better, but you're right,
                                                    > getting it in the sender's local with an offset can give more
                                                    > information. So of course it's up the the partners. Another
                                                    > option is to include the offset in another field of the record,
                                                    > whatever your data is.

                                                    No keep it all together in one data item, otherwise someone may forget
                                                    to include part of it in their calculation.


                                                    > Something else that has caused me sleepless nights is this: if I get
                                                    > a value of, say; "2004/10/12T12:34:56-08:00" mightn't that mean that
                                                    > the event occurred (or will occur) at "2004/10/12T12:34:56" UTC, but
                                                    > at a locale with an offset of "-08:00".

                                                    No. It says that the stated time IS already 8 hours behind UTC.

                                                    2004-10-12T12:34:56-08:00 is the same as 2004-10-12T20:34:56UTC


                                                    > It seems best that if two pieces of information are required,
                                                    > they should be in separate fields.

                                                    No. The Date-Time-Zone should be one piece of data.


                                                    > I agree with your point about the usefulness of knowing the
                                                    > sender's time zone. That usefulness remains even if there is
                                                    > the possibility of a one hour DST ambiguity at certain times
                                                    > of year, as I have a general sense of local business hours
                                                    > in UTC time.

                                                    That was one of my concerns. I'm still not sure that someone asked to
                                                    attend a meeting at 09:00+0100 will arrive at the right time if their
                                                    timezone is actually +0000.

                                                    Heck, most ISPs can't even set the Date/Time and Offset on their
                                                    servers correctly.




                                                    On 2004-Oct-19 Klaus Schmid wrote:

                                                    > The notation of EU25 instead of EU+01 and US18 instead of US-06
                                                    > should actually avoid the confusion caused by signed numbers. EU25
                                                    > and US18 are _names_. Names according this scheme contain
                                                    > information about the minimum UTC-offset.

                                                    I don't like adding extra data which conveys no extra information. The
                                                    ISO 8601 time zone format of -0600 for a place 6 hours behind UTC and
                                                    +09:30 for a place 9 and a half hours ahead of UTC works just fine for
                                                    the purposes which it was intended.

                                                    I assume that the EU is for Europe. What about places in Africa on the
                                                    same zone?

                                                    The US is for North America? Some places in South America have the
                                                    same Zone, but opposite DST rules.

                                                    Some places, of the same longitude, have NO DST rules. How do you cope
                                                    with that?




                                                    On 2004-Oct-19 John Steele wrote:

                                                    > We did not consult Mexico or Canada in passing our law; they simply
                                                    chose to adopt it, and any of the three could change independently,

                                                    Don't forget that since the US time zones go to and from DST at 02:00
                                                    local time for the zone that they are in, then they logically do not
                                                    all change at the same time! They change an hour apart, one hour after
                                                    each other as you move from East to West.

                                                    You can see that in action in the DST Transtions List that I linked to
                                                    above.




                                                    On 2004-Oct-24 Klaus Schmid wrote:

                                                    > Which notation would children learn easier?
                                                    > E.g. if they had to convert calendar times

                                                    > 20:00 US18 into timescale EU25
                                                    > resp.
                                                    > 20:00 US-06 into timescale EU+01

                                                    I don't think that children would be being taught about time zones at
                                                    all, at that age.

                                                    The +0600 and -0500 system is easiest as the negative number shows how
                                                    many hours behind UTC that place actually is.

                                                    At 15:00 UTC the local time at the place using" xx:xx-0600", is,
                                                    ummmmmm, 09:00!



                                                    Cheers,

                                                    Ian.


                                                    [2004-11-02]
                                                  • hjwoudenberg@aol.com
                                                    In a message dated 11/2/2004 1:09:20 PM Central Standard Time, g1smd@amsat.org writes: ... There is a handy list over at:
                                                    Message 25 of 28 , Nov 2, 2004
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                                                      In a message dated 11/2/2004 1:09:20 PM Central Standard Time, g1smd@... writes:
                                                      On 2004-Oct-07 Tex Texin wrote:

                                                      > I agree with you that time zone and daylight savings are very
                                                      > difficult to work with and change in unpredictable ways at times.

                                                      There is a handy list over at:  http://timeanddate.com/time/dst2004b.html

                                                       
                                                      Does anyone know a list of the rules for other than the US and Europe.
                                                      The rules would avoid changing the date and time twice a year.
                                                       
                                                      Herman
                                                    • johnmsteele
                                                      ... Europe. ... There was a thread starting at message #801 earlier. Perhaps the most ... From: Gilbert Healton Date: Wed Mar 10, 2004
                                                      Message 26 of 28 , Nov 2, 2004
                                                      • 0 Attachment
                                                        --- In ISO8601@yahoogroups.com, hjwoudenberg@a... wrote:
                                                        >
                                                        > >
                                                        > Does anyone know a list of the rules for other than the US and
                                                        Europe.
                                                        > The rules would avoid changing the date and time twice a year.
                                                        >
                                                        > Herman

                                                        There was a thread starting at message #801 earlier. Perhaps the most
                                                        useful is post from #852 partially quoted:
                                                        -------------------------
                                                        From: "Gilbert Healton" <ghealton@e...>
                                                        Date: Wed Mar 10, 2004 10:20 am
                                                        Subject: Re: DayLight Savings Time Changes

                                                        Visit the keepers of the TZ time-zone file at:

                                                        http://www.twinsun.com/tz/tz-link.htm

                                                        They have a data base for all current time zones, including daylight
                                                        savings time rules, and more.
                                                        --------------------------
                                                        I looked at this and tried to make sense of it. Unfortunately, it
                                                        tries to cover all the rule changes back to 1925 or so. If you look
                                                        at current rules, you (at least I concluded) conclude:
                                                        1) Rules are made to be broken
                                                        2) US, Canada, Mexico, EU, Russia and former USSR satellites, and
                                                        Australia have pretty stable rules
                                                        3) Middle East has unstable rules, and one country/one rule.
                                                        4) Israel and Brazil have annual decrees, no obvious way to predict.
                                                        5) Not too many Southern Hemisphere countries observe DST, and I
                                                        couldn't see much pattern or attempt to follow same rule over large
                                                        areas, seemed to be one country/one rule, and not too stable either.

                                                        Except for the countries in (2), I think a lot of rule checking is
                                                        needed to make sure the rules don't change.
                                                      • Klaus Schmid
                                                        ... To my experience many people even if they have frequent international contacts do not think or talk in UTC but merely in time differences between different
                                                        Message 27 of 28 , Nov 2, 2004
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                                                          On 2004-11-02 g1smd_amsat_org wrote:

                                                          >Even worse is arranging say a conference call between several offices
                                                          >in the US,
                                                          >UK, Hong Kong and Japan.

                                                          >All have offices that are open from 9am to 5pm in their local time.ody

                                                          >The only way to be sure that everyone arrives at the same time is to
                                                          >talk in UTC.

                                                          >There are hundreds of places on the net where you can find the
                                                          >date/time in UTC to a fraction of a second, any time of the day or night.

                                                          To my experience many people even if they have frequent international
                                                          contacts do not think or talk in UTC but merely in time differences between
                                                          different locations. If you know the time difference A-B and B-C you
                                                          calculate easily A-C without knowing anything about UTC. If there is any
                                                          kind of headquarter within an international company one can assume anybody
                                                          knows his time difference to the location of the headquarter, which then
                                                          acts similar to UTC. Of course I agree with the usefulness of UTC in
                                                          general, although it is not very popular in my environment. More popular in
                                                          general, including web pages, are time zone names and abbreviations like CET
                                                          and CEST.

                                                          There is no doubt about the huge amount of information about timezones, DST
                                                          and time conversions. But actually I believe there should be an easier way
                                                          without more or less extensive research. My proposal is to introduce named
                                                          timescales. If the contact information contains the timescale, nobody needs
                                                          to search for countries, cities, timezones, and DST rules. Given the
                                                          timescale we need not a huge database or library to convert calendar times,
                                                          but only few data and functions. Do we force anyone to figure out our phone
                                                          prefix number by our postal address? ISO8601 does not cover the difference
                                                          between local time and UTC but only the difference between the _indicated_
                                                          local time and UTC. Therefor an extension is needed.

                                                          >I don't like adding extra data which conveys no extra information. The
                                                          >ISO 8601 time zone format of -0600 for a place 6 hours behind UTC and
                                                          >+09:30 for a place 9 and a half hours ahead of UTC works just fine for
                                                          >the purposes which it was intended.

                                                          ISO8601: offset for indicated time
                                                          timescale: offset for any time

                                                          >I assume that the EU is for Europe. What about places in Africa on the
                                                          >same zone?

                                                          EU is for the DST rules introduced by the European Union. Others may adopt
                                                          these DST rules with the same or any other minimum UTC offset.

                                                          >The US is for North America? Some places in South America have the
                                                          >same Zone, but opposite DST rules.

                                                          timescale = DST_rules + Minimum_UTC_offset

                                                          >Some places, of the same longitude, have NO DST rules. How do you cope
                                                          >with that?

                                                          DST_rules == "C" (constant offset)

                                                          >Don't forget that since the US time zones go to and from DST at 02:00
                                                          >local time for the zone that they are in, then they logically do not
                                                          >all change at the same time! They change an hour apart, one hour after
                                                          >each other as you move from East to West.

                                                          Yes, therefor US DST rules are better suited for worldwide adoption than EU
                                                          DST rules.

                                                          >I don't think that children would be being taught about time zones at
                                                          >all, at that age.

                                                          If something can be understood by children it is more likely to be used by
                                                          more people -- including those with less education and skills -- with less
                                                          probability of errors.

                                                          >The +0600 and -0500 system is easiest as the negative number shows how
                                                          >many hours behind UTC that place actually is.

                                                          Traditionally timezones are also designated by letters. I think it depends
                                                          much on what you are accustomed. Regarding my proposal for named timescales,
                                                          probably a clearly different naming scheme could actually avoid
                                                          misinterpretations, e.g.:

                                                          EU+01 == EU time + 1h or Europe with 1h UTC offset ?


                                                          Thank you for your comments.
                                                          -- Klaus
                                                        • g1smd_amsat_org
                                                          ... There isn t a preset rule in many places. Things are decided from year to year as they go along. Some countries haven t even announced their DST
                                                          Message 28 of 28 , Nov 3, 2004
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                                                            On 2004-Nov-02:


                                                            >> There is a handy list over at:
                                                            >> http://timeanddate.com/time/dst2004b.html

                                                            > Does anyone know a list of the rules for other than the US and Europe.

                                                            There isn't a preset "rule" in many places. Things are decided from
                                                            year to year as they go along. Some countries haven't even announced
                                                            their DST transition dates for 2005 as yet - and there are less than 2
                                                            months left of 2004: http://timeanddate.com/time/dst2004b.html



                                                            On 2004-Nov-03 Klaus Schmid wrote:

                                                            >> If you know the time difference A-B and B-C you
                                                            >> calculate easily A-C without knowing anything about UTC.

                                                            Last week, my difference from someone in Australia was 8 hours. This
                                                            week it is 10 hours.

                                                            They just advanced from +0900 to +1000 for their Summer, while we
                                                            changed from +0100 to +0000 for our UK Winter. On the night of the
                                                            changeover, there were a few hours where the difference was 9 hours as
                                                            they moved first, and we moved a few hours later.

                                                            A daily conference call would have been fun to schedule during all of
                                                            that.


                                                            Cheers,

                                                            Ian.



                                                            [2004-11-03]
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