Perhaps because I'm of an evil bent, I'd love to be able to check what the moon phases were at any particular time.
Playing an Aeridinite, this could be very nice to know...
As a GM, it could be just a great way to co-ordinate evil deeds
Wouldn't it be nice if people automatically got nervous at certain times, knowing that the moon/s were full/dark?
How it could be synchronised with the real world, is a harder question though.