Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Comparison of American and Canadian football
In American football, the offensive team must run a play within 25 seconds of the referee whistling the play in – except in the NCAA (college) and the NFL where teams have 40 seconds from the end of the previous play, or 25 seconds following a penalty or timeout. In Canadian football, teams have 20 seconds regardless of the preceding situation.