UTC questionnaire

D. J. Bernstein djb at cr.yp.to
Sun Dec 5 01:43:26 UTC 1999

Markus Kuhn writes:
> The bulk of UNIX software also uses a fixed formula to break the time_t
> value down to a decomposed yyyy-mm-dd hh:mm:ss time.

That ``formula'' is isolated in a few lines of code that are invoked by
the rest of the system. New calendar rules, new time-zone systems, etc.
don't require changes except in those few lines of code.

In contrast, there are thousands of lines of code that add or subtract
time counters to handle real-time differences. This code wouldn't work
correctly if the UNIX kernel were modified to follow the POSIX rules.
You claim that nobody would notice, but I've seen several complaints
about wobbly clock behavior from people who use xntpd to reset their
time counters after leap seconds.

The bottom line is that I'm running several UNIX systems that provide
accurate civil-time displays and accurate real-time differences; I only
had to fix a small amount of code. Your systems, on the other hand, have
inaccurate civil-time displays and inaccurate time differences; your
unimplemented ``solutions'' would require massive code changes.


More information about the tz mailing list