> theoretically be represented the same way using base-60, i.e.

12:59:59:59.

I was about to say:

But that's _not_ base-60! That's base-10 used to show a value in the

range of 0 ... 59.

However, I think I (finally) see what you're getting at (that's "you"

plural because I've been working on a reply to something else all day

and making no headway). (Would "youse're" be OK in this context?)

<aside>

By the way, that reply began...

>> I just don't agree with the use of the word "base" in this

context

>

> Is radix OK

Unfortunately, according to Merriam-Webster.com,

"

Radix

1 : the base of a number system or of logarithms

"

So it seems they mean the same thing.

</aside>

If it's base-60, there must be sixty numerals, and a value in the

range of 0 ... 59 requires only one digit. So, the question is, what

sixty thingamabobs can be used to represent these sixty numerals, yet

still fit ISO 8601?

I think you're saying (or hinting, or I'm on my own) that we can use

the numerals 00, 01, 02, ... 59, which to the untrained eye look an

awful lot like two base-10 digits.

(Borrowing from the common use of 0 ... F for base-16 numerals, where

the A ... F look like alphabetic letters.)

That's ingenious!

All we have to do is cheat and say something like, "In the absence of

glyphs for these numerals in the repertoire, we'll use two

appropriate existing glyphs (0 ... 9) to stand in for the required

glyphs". (But with more authority.)

A similar tactic may be used for hours, days, months, weeks, whatever.