Quote:
Originally Posted by
filosophizer
Question:
CST6CDT (POSIX) and America/Chicago (Olson)
I have read both are same timezones, so what difference does it make?
Counter question: what is the difference between "17 (octal)" and "15 (decimal)" and "F (hex)"?
POSIX and Olson are two ways of describing a timezone. Olson does so by using a list of definitions and specifiyng a certain entry in that list. POSIX achieves the same in a slightly different way (see the Open Groups website for details).
Every timezone definition contains the following information:
1) an offset to GMT (or UTC, which is basically the same)
2) an amount of time (in hours) to correct this basic offset during the daylight savings period
3) a starting- and ending date (and time) for this DST period
In this regard, Olson and POSIX do the same. Olson just has a directory of such definitions, so that i.e. "Europe/Vienna" means GMT-1, a daylight savings adjustment of 1 hour and a DST period from the third(?) Sunday of March, 2:00 am until last Sunday in October, 3:00 am. When you specify "Europe/Vienna" then the driver looks this information up in the directory and sets the time accordingly. If you specify the TZ specification manually (the POSIX way) it uses that.
I hope this helps.
bakunin