I wonder if there could have been a problem with the time server.
I had exactly the same problem, on exactly the same day, despite the
fact that my linkstation (totally standard) has been up and running
properly for the past four months. (The only reason I noticed it was
that the ls failed to enter sleep mode on 1 August. When I checked, I
found the date to be 1 Jun 02, and the clock was several hours slow.
If it had not been for the sleep mode failure, I would never have
The time server I use is 126.96.36.199.