Comparison of American football and rugby union
A rugby union game is divided into two halves of 40 minutes (or shorter for lower-grade games, and breaks given halfway through each half if playing conditions are considered to be extreme) separated by a half time period of up to 15 minutes in an international match. Most notably, a rugby union game will continue after the scheduled end of a half (half-time or full-time) until the ball becomes dead - any occurrence that would have play restart with a scrum or lineout, or when a team scores. This has led to some "nail-biting" finishes where teams losing by only a small margin work their way towards scoring, and games can go on several minutes over time. Something similar can occur at the end of either half in American football, though usually for only a few seconds of additional time, because a play that begins before the half expires continues until the ball is dead regardless of whether there is any time left on the clock. In both sports, the clock is also stopped during substitutions and for injuries, so the referee does not need to add stoppage time as is done in soccer/Association football. American football games are made up of four quarters of 15 minutes each (less at the high school and youth levels), but the clock stops and starts according to specific rules, so that a 15-minute quarter lasts much longer.
Delay of game
The foul known as "delay of game" in American football is called "time count" in Canada. It is generally identical to the American foul, with two important exceptions. First, Canadian football only allows the offensive team 20 seconds from the referee's signal to put the ball in play, as opposed to the longer periods allowed in the American code. Second, the penalty, which is identical to that in the American code during most of the game, including convert attempts at any time, is dramatically different after the Canadian code's three-minute warning near the end of each half. After the three-minute warning, the base penalty becomes loss of down on first or second down, instead of the regular 5 yards. On third down (the final down that the offensive side has to gain a first down), the penalty becomes 10 yards with the down repeated. The referee also has the right to give possession to the defensive team if he deems repeated time count violations on third down to be deliberate.