American football
Football games last for a total of 60 minutes in professional and college play and are divided into two-halves of 30 minutes and four-quarters of 15 minutes. High school football games are 48 minutes in length with two-halves of 24 minutes and four-quarters of 12 minutes. The two-halves are separated by a halftime period, and the first and third quarters are also followed by a short break. Prior to the start of the game, the referee and team captains for each team meet at midfield for a coin toss. The visiting team is allowed to call 'heads' or 'tails'; the winner of the toss is allowed to decide between choosing whether to receive or kick off the ball or choosing which goal they want to defend, but they can also defer their choice until the second half. The losing team, unless the winning team decides to defer, is allowed to choose the option the winning team did not select, and receives the option to receive, kick, or select a goal to defend to begin the second half. Most teams choose to receive or defer, because choosing to kick the ball to start the game would allow the other team to choose which goal to defend. Teams switch goals following the first and third quarters. If a down is in progress when a quarter ends, play continues until the down is completed.
National Football League on television
Since 1998, early games have the precise, official start time of 1:01 p.m. ET, which allows for one network commercial and the NFL broadcast copyright teaser animation. However, game times are generally advertised simply as 1:00 p.m. starts. In addition, the league revised the late games to start at 4:05 p.m. ET if it was the only game televised by the network that week and to start at 4:15 p.m. ET if it was part of a doubleheader. The additional 15 minutes for doubleheaders allowed the early games extra time to be shown to completion, and avoid continuing past the late game's scheduled kickoff. For single games, only 5 minutes were added to allow the network time for a short introduction (as three hours had passed since the pre-game show has aired) and one commercial break before kickoff. In those cases there is no need to avoid early-game overlap as there is no early game shown. In addition, it allows those games to end earlier.