linguistic:translation
Time of play

Collegiate and professional football games are 1 hour long, divided into four quarters of 15 minutes each. In high school football, 12-minute quarters are usually played. However, the game clock is stopped frequently, and a typical college or professional game can exceed three total hours. The referee controls the clock and stops it after any incomplete pass or play that ends out of bounds, a change of possession of the ball from one team to the other, field goal tries, and kickoffs. In addition, each team is allowed three timeouts each half that may be used at their discretion. The clock normally runs during the action of plays, with a few exceptions known as untimed plays. Some high schools employ a mercy rule in which the clock runs continuously after one team's lead over the other achieves a certain number of points. In these instances, the clock only stops for injuries and timeouts called by a team or a referee.