official sunset/sunrise

Since most of us that fly cross country (or locally as weel), and are
restrained by the FAR's to be on the ground before sunset assuming
that we don't have position lights. Since most of us use some kind of
navigational devise (SeeYou, Glide Navigator, WinPilot etc.), I am
wondering if any of these programs utilize some data showing sunset at
the region one happens to be in? I am running WinPilot, and not aware
of of any data availabe in conjunction with it. What is everybode else
doing?? 6PK