Jon Udell's "A literary appreciation of the Olson/Zoneinfo/tz database" points out the transcendentally complex nature of keeping track of every timezone and temporary change in times that exists today or has existed in the past. I've spent hours poring over this file and have to concur with John — it's probably the most fascinating reading on your hard-drive.
What I didn't appreciate, until I finally unzipped and untarred a copy of ftp://elsie.nci.nih.gov/pub/tzdata2009o.tar.gz, is the historical scholarship scribbled in the margins of this remarkable database, or document, or hybrid of the two.
You can see a glimpse of that scholarship in the above example. The most recent two rules define the latest (2007) change to US daylight savings. The spring forward rule says: "On the second Sunday in March, at 2AM, save one hour, and use D to change EST to EDT." Likewise, on the fast-approaching first Sunday in November, spend one hour and go back to EST.
But look at the rules for Feb 9 1942 and Aug 14 1945. The letters are W and P instead of D and S. And the comments tell us that during that period there were timezones like Eastern War Time (EWT) and Eastern Peace Time (EPT). Arthur David Olson elaborates:
From Arthur David Olson (2000-09-25):
Last night I heard part of a rebroadcast of a 1945 Arch Oboler radio drama. In the introduction, Oboler spoke of "Eastern Peace Time." An AltaVista search turned up :"When the time is announced over the radio now, it is 'Eastern Peace Time' instead of the old familiar 'Eastern War Time.' Peace is wonderful."
Most of this Talmudic scholarship comes from founding contributor Arthur David Olson and editor Paul Eggert, both of whose Wikipedia pages, although referenced from the Zoneinfo page, strangely do not exist.