[tz] tz abbreviations / zdump for programmers

Dave Cantor dave at davecantor.us
Tue Jun 5 21:27:46 UTC 2012

The ambiguity over what is standard time in the U.S. is not 
helped by the actual law, which uses the word 'standard time' 
without capital letters to refer to whatever time is the legal 
time in a zone.  I other words, if I understand this correctly, 
the standard time on the west coast right now is Pacific Daylight 
Time, and the standard time during December, e.g., will be 
Pacific Standard Time.    See the actual regulation at
"http://tycho.usno.navy.mil/260.html", sections 260 through 265.

So when a person says that something will occur at 7:30 pm xx 
standard time, they may mean according to the wall clock at that 

Dave C.

On 05-Jun-2012, John Haxby wrote:

> On 5 Jun 2012, at 18:46, Dafydd Rhys-Jones wrote:
> > If I recall, correctly, PST/PDT is Pacific Standard Time, and
> > Pacific Daylight Time in the US.
> > 
> You are, of course, correct.   It was my misfortune to work with
> someone who insisted that a meeting was going to be at Pacific
> Standard Time, that meeting was arranged a few *before* daylight
> savings began in Spring for a date a few days after.   We checked,
> yes, she did mean PST and she got quite heated about it.  We
> ignored that and decided to schedule the meeting for PDT anyway as
> the UK clocks hadn't changed so it made a difference to us.
> It's not just that one person, I've since come across others who
> think that it's PST all year round, sometimes with daylight
> savings in force, sometimes not.  It's not that long ago that
> someone thought we in the UK were on GMT all year round.    US TV
> often advertises programs starting at some time ET (eastern), MT
> (mountain) or PT (pacific) without any reference to daylight
> savings.   This actually makes sense but may contribute to
> confusion.
> Asking people to provide a timezone for the purposes of, for
> example, scheduling meetings, is a minefield.  Especially around
> the vernal and autumnal time changes.   Subscribers to this list
> are in a minority in understanding timezones!
> jch
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