A space-time tracker for announcing the time and tracking the celestrial bodies on the spot of observation comprises a clock mechanism with clock hands on a dial of 24 hours and a synchronic motor for driving a star atlas and a plurality of planet driving devices which actuate a plurality of annular displays moving around a moon/star ring to periodically show an on spot planet thereon. The space-time tracker also indicates the variations or deviations of the solar calendar and the lunar calendar and the times of different time zones around the world. This disclosure is characterized in automatically and perfectly demonstrating the relationship between the time and space.