*Discount through Halloweeen*
Ive always been fascinated by the solar terminator - the line dividing day and night.
Daylight draws the terminator on a map of the world, and shades in the areas of the world where its night - by default, it draws the current terminator, but you can specify the exact time for which the terminator should be drawn.
If you want to see in more detail, turn your device sideways for a scrollable, zoomable map.