Beginner questions

Guy Harris guy at
Wed May 26 21:12:24 UTC 2004

On May 26, 2004, at 11:23 AM, Ruby Ballen wrote:

> Well, yes. What I was trying to say is if it is possible to do this:
> - When the user enables automatic DST calculations, use the regular 
> rules.
> - When the user disables automatic DST calculations, compute local 
> time using the offset that the
> time zone has when it is in standard time, regardless of DST being in 
> effect or not.

Yes.  As Paul Eggert said in his reply:

>> 2) Is it possible to disable DST changes when using this library?
> Sure; use (for example) TZ='MST7', which means to always use Mountain
> Standard Time without daylight-saving.  Such a setting would be
> appropriate for Phoenix, Arizona after 1968, for example.

Setting the TZ environment variable will affect only processes with 
that setting; for example, if you set it in a UN*X shell, the shell and 
the processes it creates will use that setting.  That won't affect 
other processes on the system, e.g. system daemons; you'd have to 
change some global time zone setting (however that's done on your 
particular system) to do that.

Note, however, that this does *NOT* let the user "move the clock 
forward/backward manually when DST is in effect", if by "the clock" you 
mean the system clock - on UN*Xes, the clock doesn't get moved when DST 
starts or ends, as Garrett Wollman noted.

What is the exact thing you're trying to do here?

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