Here the game time is separated into two basic domains: the main time and the overtime. To switch between the two requires some trigger event, often the expiration of the main time. In chess, reaching a fixed number of moves can trigger the gain of a fixed amount of extra time. This usually occurs in long games after the 40th move: e.g. 120 minutes to complete the first 40 moves, and another 30 minutes to complete the rest of the game.