Re: [MacPerl-Porters] MacPerl daylight saving time issue

At 18:35 Uhr +0000 15.09.2002, Peter Prymmer wrote:

>While I cannot comment on any possible problem in GUSI I can
>tell you that the message regarding Unix and Windows behavior
>from Steffen is incorrect.  24 December 2001 may have $dst == 0
>for many Northern latitudes, while it may have $dst == 1 for many
>Southern lattitudes (i.e. those south of the equator).
>
>The settings of daylight savings time is a political matter
>and rather difficult to capture accurately in computer
>programming, since among other things laws regarding the
>setting of daylight savings times depends on laws that
>may be written well after an operating system or programming
>language is released.  At least on Unix the rules are
>easily amended by careful placement of symlinks in the
>filesystem (at linux implements it that way).
>
>For "convenient" examples of how complex the rules can be
>try to determine the GMT offset of eastern and western
>Indiana in the US for different dates.  Now do the same
>exercise for each of the Australian states (they have
>30 minute and 45 minute offsets from the hours GMT offset).
>
>For what it is worth I think that the result you obtained
>is perfectly fine for e.g. Sydney on 24 Dec 2001.
>
>Peter Prymmer

Thanks, Peter. To clarify things: Steffen said, that the DST setting 
on Unix and Windows depends on a given date. I think this is 
absolutely correct. I have provided the Christmas Eve example, and it 
was bad example, I must confess, now that I have read your email. As 
it happens sometimes, a problem that seems to be trivial, turns out 
to be very complicated.


Best regards,

Thomas.