EarthDesk is a really curious application that changes your wallpaper and set a new dynamic one featuring the real world map.
That world map features the evolution of day and night in Earth.
By that way, you'll know at a glance if it's day or night in any place in the world.
Choose political map or physical map and you'll have all the Earth at your sight.
Finally, you can also apply layers with weather information.
Restrictions:
Trial version with some functions disabled and watermark.
