Editing Go (game) (section)

=== Time control ===
{{See also|Time control|Byoyomi}}

A game of Go may be timed using a [[game clock]]. Formal time controls were introduced into the professional game during the 1920s and were controversial.{{sfn|Bozulich|2001|pp=92–93}} Adjournments and [[sealed move]]s began to be regulated in the 1930s. Go tournaments use a number of different time control systems. All common systems envisage a single main period of time for each player for the game, but they vary on the protocols for continuation (in ''overtime'') after a player has finished that time allowance.{{efn|1=Roughly, one has the time to play the game and then a little time to finish it off. Time-wasting tactics are possible in Go, so that ''sudden death'' systems, in which time runs out at a predetermined point however many plays are in the game, are relatively unpopular (in the West).}} The most widely used time control system is the so-called [[byoyomi]]{{efn|1=Literally in Japanese ''byōyomi'' means 'reading of seconds'.}} system. The top professional Go matches have timekeepers so that the players do not have to press their own clocks.

Two widely used variants of the byoyomi system are:<ref name="Byoyomi">{{Citation | publisher = European Go Federation | url = http://www.eurogofed.org/egf/tourrules.htm | title = EGF General Tournament Rules | access-date = 2008-06-11}}</ref>
* ''Standard byoyomi'': After the main time is depleted, a player has a certain number of time periods (typically around thirty seconds). After each move, the number of full-time periods that the player took (often zero) is subtracted. For example, if a player has three thirty-second time periods and takes thirty or more (but less than sixty) seconds to make a move, they lose one time period. With 60–89&nbsp;seconds, they lose two time periods, and so on. If, however, they take less than thirty seconds, the timer simply resets without subtracting any periods. Using up the last period means that the player has lost on time.
* ''Canadian byoyomi'': After using all of their main time, a player must make a certain number of moves within a certain period of time, such as twenty moves within five minutes.<ref name="Byoyomi" />{{efn|1=Typically, players stop the clock, and the player in overtime sets his/her clock for the desired interval, counts out the required number of stones and sets the remaining stones out of reach, so as not to become confused. If twenty moves are made in time, the timer is reset to five minutes again.}} If the time period expires without the required number of stones having been played, then the player has lost on time.{{efn|1=In other words, Canadian byoyomi is essentially a standard chess-style time control, based on ''N'' moves in a time period ''T'', imposed after a main period is used up. It is possible to decrease ''T'', or increase ''N'', as each overtime period expires; but systems with constant ''T'' and ''N'', for example 20 plays in 5&nbsp;minutes, are widely used.}}