Sun Clock is a program for Windows to show the local time around the world and the areas of the globe which are in night or day.The surface of the world is represented using satellite imagery from the NASA Goddard Space Flight Centre enhanced with 3D terrain data to give a colourful portrayal of the physical geography of the planet. The image has been enhanced to change subtly throughout the year reflecting the seasonal advance and retreat of ice caps, snow cover.The moving shadow covers the area on the globe where the sun is below the horizon. Where neither the sun nor the moon can be seen, the shadow is darker still.As an area becomes covered by the night-time shadow, town and city lights are turned on. Their brightness is in proportion to the population size.You can overlay the maps with an image of global cloud cover. The clouds layer makes use of public domain satellite photographs. The images are updated approximately every three hours. However, the cloud layer is dependent on NASA, The University of Dundee, and XPlanet, so the quality and the continuing availability of the service is beyond our control.