<P> A team on defense has little control over the pace of the game . It may expend its timeouts to ensure that there is adequate time left on the clock, in case the team regains possession . The defense can make decisions on how to stop the ball carrier based on whether the team is trailing or leading: if the offense is trying to conserve time, the defense can foil that by tackling the ball carrier in - bounds before they can get out of bounds . Defenses likewise can safely devote more personnel to the perimeter and leave the center of the field less defended, as an offense that cannot afford to keep the clock running will have to throw toward the sidelines . Various rules ensure that the defense cannot deliberately commit fouls to manipulate the game clock, and in the most extreme such cases, an unfair act can be declared and the game forfeited to the offense . (Likewise, if the offense commits fouls to burn off time and get extra downs, the clock is reset and unsportsmanlike conduct is called on them .) </P> <P> In Canadian football, a team trailing by one point or tied has an additional option: a ball can be kicked from anywhere on the field in that sport, and balls kicked into or through the end zone and not returned score a single point . This allows a team trailing by one to advance the ball upfield, then punt the ball toward the end zone in hopes of tying the game for one point (the player could also drop kick the ball, which would allow the kicking team to win on a field goal if kicked through the uprights). To prevent this scenario, defending teams will place their punter in the end zone to retrieve the ball and kick it back out of the end zone, preventing that single point from being scored . </P> <P> Several of the strategies discussed above for American football above can be used in the Canadian code, however rule differences mean that running out the clock much more difficult: </P> <Ul> <Li> Teams are allowed only three downs to advance the ball 10 yards without losing possession (as opposed to four in the American game). </Li> <Li> The offensive team has only 20 seconds after the ball is whistled into play to start a new play (as opposed to 25 seconds in American high school football and 40 seconds from the end of the last play in college football and the NFL). </Li> <Li> After the three - minute warning in Canadian football, two key timing changes occur: <Ul> <Li> The clock stops after every play . The clock restarts when the referee whistles the ball in play after a tackle in bounds, and with the snap after an incomplete pass or a tackle out of bounds . </Li> <Li> A "time count" (the same foul as "delay of game" in American football), which is a 5 - yard penalty (with the down repeated) at other points in the game, becomes a loss of down penalty on first or second down and a 10 - yard penalty on third down . Additionally, if the referee deems a time count violation on third down in the last three minutes of a half to be deliberate, he can require the offensive team to legally place the ball in play within the 20 - second count, with a violation resulting in loss of possession . </Li> </Ul> </Li> <Li> If the clock hits 0: 00 between plays, Canadian teams are required to execute one final play, even if the ball has not yet been snapped . In the American game, if the clock hits 0: 00 between plays, the game is over unless the previous play ended in a defensive penalty, a score, or circumstances warranting various types of kicks . </Li> </Ul>

When does clock stop for out of bounds in nfl