[time-nuts] How best to compute local time from GPS

[Morris Odell]

David Forbes asked:

>> 2. If I have to store the time zone from the user's input, are the
>> DST calculations reasonably straightforward these days?

It's not too difficult and you get a nice refresher in modulo-7 arithmetic. 
I did it in AVR assembler recently although I didn't try to make it 
universal. Our government down here in south-eastern Australia recently 
changed the DST changeover dates so I customised it for where I live. If you 
need to make it user settable that would mean you need to be able to enter 
the dates and UTC offsets as a menu item which would complicate things 
considerably. It'd be a fun programming challenge though :-)

>> 4. In general, is it better to let the user turn DST on and off or
>> try to do it automatically? (I live in Arizona, which doesn't worship
>> DST, so I have no experience in this matter.)

I put a 3 position (centre off) switch on the back panel of my clock. The 3 
positions are: Summer time, Auto, Winter time. That way after I'm demented 
or dead and gone if the gov't changes the rules again it can be changed 
manually.

I programmed the receiver for our local time offset from UTC. I then add or 
don't add an hour as the case may be.

Morris