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.
Half-time
While it exists mainly to allow competitors to rest briefly and recover from the play of the first half, half-time also serves a number of other purposes. It also serves as an intermission for spectators, and it often features entertainment, such as cheerleading performances, tifos, performances by school marching bands (particularly in high school and collegiate sports in North America), or concerts featuring popular music acts (particularly in major events, such as the Super Bowl). On games that are broadcast on television and radio, it also provides broadcasters with an opportunity to give a recap of the first half of the game, air highlights of other games in progress, air commercials and other advertisements, provide analysis on the game, or air game-related festivities (such as an aforementioned half-time performance). In the NFL (National Football League), halftime is usually around 12 minutes, although for major events like the Super Bowl it may last much longer to allow for more activities like musical performances.