FW: tz interface problems

Garrett Wollman wollman at khavrinen.lcs.mit.edu
Wed May 20 14:54:43 UTC 1998

<<On Wed, 20 May 1998 09:47:42 -0400, "Olson, Arthur David"
<OLSONA at dc37a.nci.nih.gov> quoted a message from D. J. Bernstein:

> The practical effect is that many systems slipped by a second in 1997,
> and will probably slip by another second at the end of 1998.

FreeBSD follows the PCTS/xntpd model of leap second observance (which
is to say, ``it doesn't'').  We actually care more about NTP working
than PCTS, so until NTP is redesigned to tick TAI, or the NTP daemon
redesigned to deal with a leap-second-cognizant operating system,
we're stuck with it.

In any case, if the user enabled leap seconds, that means they already
have the source and were capable of editing the Makefile and
reinstalling the timezone data files.  It would not be particularly
difficult for us to add an additional installation option, ``install
timezone source files'', just as we do for the sendfail config kit,
but this would not be meaningful to 99% of our new-installation users,
and those who care are the sort who would install the source anyway.

If we really wanted to deal seriously with leap seconds, we would
probably add the functionality to libcalendar.  There are essentially
three ways one would want to use this information:

- for any given time, compute the value of TAI-UTC
- for any given time, compute the difference between UTC and POSIX time
- convert a specific UTC, POSIX, or TAI time into one of the other systems

I can't speak for other systems.


Garrett A. Wollman   | O Siem / We are all family / O Siem / We're all the same
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