mo@seismo.UUCP (Mike O'Dell) (05/10/85)
Ah yes, the old bugaboo of keeping system time in some awful local time. One of the things done right by Unix is to keep system time in GMT (or CUT as it is now known to some degree in inaccuracy) and convert using an adjustable bias when displaying it to humans. System III's predicessor started the useful hack of making this bias a per-user adjustable quantity, so if I am on the East Coast using a West Coast computer, "date" can give me "my local time". So, by keeping system time in CUT, you don't have to adjust the clock when you get off the plane - this can cause havoc with things like Make - OOPS, don't have such tools on the Mac :-)!!! You just adjust the offset for the local bias from GMT. Temporally yours, -Mike O'Dell
jeff@rtech.ARPA (Jeff Lichtman) (05/12/85)
> Ah yes, the old bugaboo of keeping system time in some awful local time. > One of the things done right by Unix is to keep system time in GMT > (or CUT as it is now known to some degree in inaccuracy) and convert using > an adjustable bias when displaying it to humans. System III's predicessor > started the useful hack of making this bias a per-user adjustable > quantity, so if I am on the East Coast using a West Coast computer, > "date" can give me "my local time". So, by keeping system time in CUT, > you don't have to adjust the clock when you get off the plane - this > can cause havoc with things like Make - OOPS, don't have such tools > on the Mac :-)!!! You just adjust the offset for the local bias from GMT. > > Temporally yours, > -Mike O'Dell This will work, but it's easy to do it wrong and paint yourself into a corner. Some parts of the world have time zones that are not an integral number of hours different from Greenwich. For instance, the middle part of Australia is 30 minutes different from its ends. If the person who wrote the configuration program didn't know this, he or she might be tempted to simply have an integer parameter to stand for the number of hours difference between Greenwich and local time. If you ever have to write software that stores time as GMT, and you ever want to sell it internationally, you would do well to remember this. -- Jeff Lichtman at rtech (Relational Technology, Inc.) aka Swazoo Koolak {amdahl, sun}!rtech!jeff {ucbvax, decvax}!mtxinu!rtech!jeff
russell@acf4.UUCP (Bill Russell) (05/14/85)
As an aside, one must note that not all computer systems will be used with the "local machine time" being equal to "local real time". I can see many applications where the system time will be UT or GMT. If someone adds these auto-switch to xDT and back to xST, they must be able to be defeated when somene is not working in an area where that makes sense. As an example think of the computers on board the Shuttles. They more than likely keep UT.
brent@phoenix.UUCP (Brent P. Callaghan) (05/17/85)
> Some parts of the world have time zones that are not an integral number of > hours different from Greenwich. For instance, the middle part of Australia > is 30 minutes different from its ends. > > If you ever have to write software that stores time as GMT, and you ever want > to sell it internationally, you would do well to remember this. > -- Can't imagine much of a market in the middle of Australia. :-) -- Made in New Zealand --> Brent Callaghan AT&T Information Systems, Lincroft, NJ {ihnp4|mtuxo|pegasus}!phoenix!brent (201) 576-3475
jcp@brl-sem.ARPA (Joe Pistritto <jcp>) (05/30/85)
Actually, for true international compatability, you have to adjust offsets in 10 minute intervals. It seems Nepal has a timezone just 10 minutes 'ahead' of Indian Standard Time, which makes it: India (all parts): +5h 30m Nepal (all parts): +5h 40m I experienced the idiocy of this myself, having to set my watch forward 10 minutes.. -JCP-