Portable general timestamp format, not 2038-limited

James Harris james.harris.1 at googlemail.com
Fri Jun 22 22:33:04 CEST 2007


I have a requirement to store timestamps in a database. Simple enough
you might think but finding a suitably general format is not easy. The
specifics are

1) subsecond resolution - milliseconds or, preferably, more detailed
2) not bounded by Unix timestamp 2038 limit
3) readable in Java
4) writable portably in Perl which seems to mean that 64-bit values
are out
5) readable and writable in Python
6) storable in a free database - Postgresql/MySQL

The formats provided by the two database systems are such as 8-byte or
12-byte values which, even if I could get Perl to work with I guess it
would be messy. Keeping to 32-bit values should give me portability
and be easy enough to work with without obscuring the program logic.
Since 32 bits of microseconds is less than 50 days I have to store two
32-bit values. How to split them? The option I favour at the moment is
to split days and parts of days like this:

a) store, as a 32-bit number, days since a virtual year zero (there is
no year zero in common era time <http://en.wikipedia.org/wiki/
Common_Era>). This allows over five million years plus and minus.
Still not completely general, I know.
b) store parts of days as another 32-bit value. Its range would have
to go to 86401 seconds - the number of seconds in a leap day. This
means each 'tick' would be around 21 microseconds. For regularity I
could make the ticks 25 microseconds so there would be 40,000 in a
second and 3,456,000,000 in a day; and, finally, the counter could
tick about 5 hours into the next day if not caught.

Any thoughts on a better way to do this? (Please reply-all. Thanks).

--
James




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