using DS1307

[Art]

Another option, depending on real natural light available, is to have the pic learn the
real daylight cycle so you never have to set the clock.
This is what some solar controllers with auto night light output do to figure out when
to turn night lights on and off.
They are designed to use on remote toilet blocks and such, and would not be subject
to getting thrown off too much by the home lights being turned on and off.

[SUNFLOWER]

I wrote a program for 18F4620 that reads time and date from DS1370 and then calculates sun position for users latitude, see Get_Path:

Code = http://www.harbornet.com/sunflower/PCB.pbp
Schematic = http://www.harbornet.com/sunflower/PCB.jpg

Time = number of minutes since midnight.

[Art]

That's commendable.