Daylight Savings Time

[Warren Seltzer]

As it happens, the project I'm working on involves a network of Unix
and non-Unix systems both running C code.  The central Unix system is
the time server, and sends time-set messages out over a network.

It also happens that the network elements need to know about Daylight
Savings Time changes *BEFORE* and *AFTER* they occur.  That is, the time
set message is  "It is now such-and-such, and we switch time in 3
hours and 2 seconds, and the switch is for +60 minutes".  Or, "... we
switched 5 hours ago and the switch was for +60 minutes", which in our
case turns out to be the important situation.

This sort of thing is necessary if you have a network that passes around
time-stamped records that are supposed to be user-compatible and viewable
at different spots in the net.  

Although we cannot of course expect C standards to pre-implement our every
application need, we can note that networks are very common these days, and
we found Unix time routines to be very helpful.

When central time servers set the time for peripheral nodes that are in
different time zones, similar requirements pop up.

                           teltone!warren
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______
 Warren Seltzer
 Teltone Corporation
 Kirkland, WA
 206-827-9626

....uw-beaver!teltone!warren