In timed play, a timer determines the length of each half of a game. The timer is conventionally called a clock.
NAQT rules are the only rules currently in nationwide use that involve timing games. Middle school and high school games use nine-minute halves. Community college games use 10-minute halves. ICT games use 11-minute halves
Timed games generally also have an upper limit on the number of tossup-bonus cycles that will be read regardless of time. (In NAQT matches the limit is currently 24 tossup-bonus cycles.)
College Bowl used timed games. Evolution away from this began in the early 1990s, with only the most purist ACF events—such as the Georgia Tech MLK and ACF Nationals—being untimed. By the turn of the millenium, the only timed tournaments remaining were NAQT Sectionals and ICT, Stanford's Cardinal Classic, Michigan MLK, and Penn Bowl, plus of course all College Bowl-run events. Cardinal Classic dropped the clock starting in 2001, Penn Bowl in 2003, and MLK in 2006. In order to better simulate the ICT environment, the 2008 and 2009 FICHTE tournaments used the clock and NAQT's 2-second recognition rule.
In general, teams playing a timed match will want to hurry if they want more tossups to be heard, or use as much time as possible if they want fewer tossups to be heard. Accordingly, a team will often hurry the game in two cases:
- The team is behind near the end of the game and needs to hear more tossups to improve its chance to come back.
- The team believes itself to be better than the other team, so hearing more tossups will reduce the likelihood of an upset.
Conversely, the other team will want to slow the game.
Under the CBI and pre-2008 NAQT rules, the half ended immediately when time expired in the middle of reading a tossup, unless a team buzzed before time expired and answered correctly (earning the team a bonus as usual in NAQT). This rule allowed a team with a small lead in the closing seconds of the game to preserve a victory with the clock-killing neg, preventing the other team from answering the tossup and getting a bonus. Since CBI is defunct and NAQT has changed its timing rules, the clock-killing neg is no longer a useful strategy. See also history of NAQT game format.
In many TV tournaments as well as at the National Academic Championship, a fixed number of questions are read, but drama is created by omitting the question numbers and slowing or speeding the reading pace in order to fill a pre-designated amount of time. Rounds at these formats are ended by a "clock expiration" noise (buzzer, whistle, conch shell, etc.) after the last question in the packet is completed.
Mainstream tournaments using the clock for the entire game as of 2020
(I.e. not TV tournaments, formats with sixty-second rounds that are otherwise untimed, etc.)