[Python-ideas] use gmtime(0) epoch in functions that use mktime()

[random832 at fastmail.us]

On Sat, Sep 6, 2014, at 13:06, Guido van Rossum wrote:
> There used to be systems with a different notion of epoch. Are there still
> such systems around? OSX has the UNIX epoch -- what's it gmtime(0) on
> Windows?

If you call the time.h functions from the CRT library, they use 1970
(and always have). Windows has _other_ functions that use a different
epoch (1600, if I remember correctly), but they're native win32
functions not called directly by python.

The wrinkle you get on windows is that most of the functions don't work
with *negative* time_t values (or struct tm values representing dates
before 1970), and/or some other arbitrary cutoff dates. In particular,
time.localtime gives an OSError on negative values, but time.gmtime
gives an OSError on values below -43200, and both give errors if passed
a value representing a year above 2999, and strftime does not accept
years above 9999.

But, as I've advocated before, there's no fundamental reason that python
should chain itself to the C library's underlying implementation rather
than defining its own time functions that do always use an epoch of
1970, and handle leap seconds consistently, have unlimited range, etc.