How is daylight savings time set?

[Brian Bainter]

I have a routine which gives me the long time number when I send it a
struct tm *.  Something that I wish UNIX provided.  The problem is, when
I give it a date that is on the other side of the DST date that I am currently
in, it gives me erroneous results.  What I need to know is, how does UNIX
compute which day in the year that it changes to DST?  If I could duplicate
this computation, I could fix my problem.

Thanks,
-- 
Brian R. Bainter  KA7TXA
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