On Mon, 9 Nov 1998 lex at cc.gatech.edu wrote:

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

No single person does ;-)
 
> 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?

Actually "absolute time" is far trickier to do right than you may imagine.
(There is no such thing as absolute time, for starters)
As it pertains to Smalltalk, witness the differences in the DateAndTime
class between ANSI Smalltalk rev 1.2 and rev 1.9.
They completely blew it.  They started of trying to do the "right" thing,
make an attempt at handling leap seconds in UTC.  But it was to difficult,
I guess, and perceived as not woth the effort, so they took it out for 1.9.
Where they blew it, is that they still call it UTC.  For people who know
time, this ranks up there with the same sloppiness that Java did.

Oh, well.  Anybody who is going to be doing anything with time that
requires (sub)second accuracy will be using there own stuff, anyway.

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

If you punt on the leap second issue, and accept what I would call
'POSIX time' (very loosely speaking, GMT), you will find that the best
time zone information tables are kept by the UNIX world.  One of the
guys who helps maintain this stuff (and knows more about time keeping
than anyone else I know could possibly care about :-), Paul Eggert,
has the following page of resources:

	http://www.alumni.caltech.edu/~mklein/timezone.html

And you thought it was going to be simple ;-)

-- Mike Klein

"Nothing works, and nobody cares"  -- Woody Allen