[DSP-10] A Clock Question

[Bob Larkin]

Hello All,

I am in the process of "unifying" the clocks used inside the DSP-10 program 
UHFA.  This is spurred on by wanting to have automatic, precision setting 
of the clock from a GPS.  I have that part more-or-less under control, but 
I am seeing complications in the handling of time zones, and particularly 
daylight time.

First a couple of comments. DOS allows for time zones through the 
environmental variable TZ, which can be read and applied.  The C routines 
use this to automatically change the offset for daylight time, if this is 
specified, i.e., "SET TZ=PST8PDT"

DOS does NOT change the computer time in April and October, it only 
automatically adjusts for it when computing GMT from local time. If you do 
not use the DOS command TIME it will be wrong.  Windows (I don't know which 
versions) allows for automatic time change, if Windows is run.

All of this becomes very simple if the TIME command is set to GMT and the 
environment is "SET TZ=GMT0"
With this, the program never checks for daylight time, and, it turns out, 
all the clock operations can run from a single software time source (the 
source that has the daylight info does not have fractional seconds, and 
visa versa).

Tell me what kind of problems running everything in GMT would create for 
people?  I have always done this, but I know others have used local time in 
some way.

Many thanks,
Bob Larkin  W7PUA

PS- It may not be obvious, but internally to UHFA GMT is a must, as it is 
needed for Moon calculations, Sun calculations, and PUA43 code stirring.