Abstract: A geographical chronological device which simultaneously indicates the time in multiple cities or countries, and displays fluctuations in day or night in a geographic location. The earth clock has a semi-transparent world map depicting a polar planetary projection of the world from the north or south pole. An adjustable shadow disk is disposed adjacent to and partly visible through the semi-transparent world map. The shadow disk has a periphery with time indicia disposed about the periphery. The adjustable shadow disk has an adjustable dark portion to indicate night and an adjustable light portion to indicate day. The dark and light portions adjust to indicate relatively greater or lesser night and day according to the change in seasons. A clock movement provides relative movement between the semi-transparent world map and the adjustable shadow disk.