> The GPS units from slickitems

> From the date returned from the GPS (e.g.. 99 10 29), I do not
> know what the day of the week it is Sun - Sat.  Is there some
> mathematical algorithm to tell me the day of week.

Convert the date into an integer "universal day", like Julian
date used for astronomical purposes.  Sometimes it's easier to
base a "new year" on March 1st (so that leap days are the very
end of the previous year).  Then take the "universal day" value
modulo 7 to get day of week.

A good reference for this is the book "Calendrical Calculations"
by Nachum Dershowitz and Edward M. Reingold.


> Or is there a way from data returned from GPS to know based
> where I am located if the time is daylight savings time or
> standard time.

The GPS unit, if working properly, knows where it is located
with great precision.  However, daylight savings time rules are
arbitrary, capricious, politically motivated, and based on
regions defined arbitrary geopolitcal boundaries (countries,
states, counties, and random exceptions).

Converting an specific lat/long locations into the proper DST
rule is the tricky part.  The task can be handled by a PIC but
the database of region boundaries is non-trivial.

                                                Lee Jones