Hi,
The POSIX timezone notation as understood by the zic code includes the possibility of zoneabbrev[+-]hh[:mm[:ss]] but the meaning is that hh:mm:ss *is* the offset from GMT, and zoneabbrev is being defined as the abbreviation for that offset. What the datetime.c code is doing is trying to find the zoneabbrev in a built-in timezone table, and then adding the two together. This is simply wacko.
I think that if anyone has ever tried to use this notation they would have noticed this misinterpretation of the specs.
Given where the code stands now, I think the best solution is to rip out DecodePosixTimezone and instead pass the syntax off to the zic code (which can handle it via tzparse()). Since the datetime input parser is ultimately only interested in the GMT offset value, this would mean that the zoneabbrev part would become a noise word.
Sounds like a good idea to me. Sander