Does anyone out there know how timezones work, in detail?

I'm interested in distinguishing "local time" and "absolute (Greenwich) time" in Squeak
Absolute time is simple enough, but the definition of local time seems more elusive.  Is everyone's local time always an integral number of hours offset from Greenwich, or can it be more complicated?  Also, where do all the names like "EST" come from?


Thanks for any input, and lots of thanks for pointers to code :)


Lex