A time control is a mechanism in the tournament play of almost all two-player board games so that each round of the match can finish in a timely way and the tournament can proceed. For turn-based games such as chess, shogi or go, time controls are typically enforced by means of a game clock, which counts time spent on each player's turn separately. A player that spends more time than the time control allows is penalized, usually by the loss of the game. Time pressure (or time trouble or Zeitnot) is the situation where one player has very little time on their clock to complete their remaining moves.
Classification The amount of time given to each player to complete their moves will vary from game to game. However, most games tend to change the classification of tournaments according to the length of time given to the players. In chess, various classification schemes are used. FIDE defines time controls based on the sum of the amount of time allotted to each player, plus the increment per move times 60. Any time control in which this sum is at least 60 minutes (120 minutes at the master level) is classical; any time control in which the sum is less than 60 but more than 10 minutes is rapid; any time control with a sum at or less than 10 minutes is blitz. Standards may differ; Lichess and Chess.com both consider 10 minute games to be rapid rather than blitz. In addition, both sites have a separate bullet category for games in which less than 3 minutes are given to each player; Lichess additionally has hyperbullet (≤30s) and ultrabullet (≤15s) categories. In Go, anything under twenty minutes could be considered "blitz".
Methodology The exact approach to using a game clock to regulate games varies considerably.
Sudden death This is the simplest methodology. Each player is assigned a fixed amount of time for the whole game. If a player's main time expires, they generally lose the game.
Overtime formats 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 added to the leftover 120 minutes to complete the rest of the game.
Penalty formats Such methods exact a points penalty, or fine, on the player who breaches their time limit. One example occurs in Go, where the Ing Rules enforce fines on breaches of main time and overtime periods. The rules may also provide for a sudden death time control in addition to the penalty. In tournament Scrabble, the time control is standardized to 25 minutes per side with a 10-point penalty for each minute or part thereof that is used in excess, so that overstepping the allotted time by 61 seconds carries a 20-point penalty; a player who oversteps by 10 minutes automatically loses; in this case, their opponent is given enough additional points to win by one point, if they were not already in the lead at that time.
Hourglass Each player's clock starts with a specified time (such as one minute or ten minutes). While one player is deciding a move, their clock time decreases and their opponent's clock time increases. This is analogous to an hourglass: sand empties from one container and fills the other. The sum of both clocks always remains the same, and slow moves give extra time to the opponent. There is no maximum amount of time allotted for a game with this timing method; if both players play quickly enough, the game will continue until its natural end. Use of this time control is uncommon.
Game formats
Go
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