[tz] zic changes (2/2)

[Paul Eggert]

Aurelien Jarno wrote:
> Are you sure you have the posixrules file installed in
> /tmp/prefix/zoneinfo/posixrules?

No, I didn't have those installed, because glibc 'make install' doesn't install 
them. Your hint let me figure out what I needed to do to reproduce the problem.

I eventually tracked this down to a bug in glibc, which Sébastien Brissaud 
reported on February 27. See:

https://sourceware.org/bugzilla/show_bug.cgi?id=19738

The bug is that glibc adds the posixrules file's first transition time (the 
minimum time_t value -2147483648) to the UTC offset -28800, and this addition 
overflows and wraps around to a large positive number.

I proposed a glibc patch here:

https://sourceware.org/bugzilla/attachment.cgi?id=9074

I don't see a good zic workaround for this glibc bug.  zic could emit a slightly 
later transition time (a day later, say), but this would cause programs to 
mishandle time stamps near the origin at 1901-12-13.