From Fulvio Castelli:
The WorldClock Screen Saver displays a high resolution day/night view of a world map. The day image has been drerived from detailed satellite images of planet Earth. Similarly, the night image is based on NASA's 'Night Lights' composite image of planet Earth. These two images are merged to create an image presenting the day and night areas of the Earth at the current ime. In addition, a calendar with many configuration options can be super-imposed on the world map. A 3D clock can also be super-imposed on the world map.