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.
American football rules
If a game is tied at the end of four quarters, "overtime" is played. In overtime, the coin is tossed to determine which team will possess the ball first. The winner of the coin toss can choose to give the ball or receive the ball. If the first possession results in a field goal, the other team is given possession to match or better the field goal; therefore continuing the game. If the first possession results in a touchdown or safety, the scoring team wins. During the regular season in the NFL, one overtime period is played (with each team receiving two time outs). If both teams are tied after the 10-minute overtime, the game officially ends in a tie. In the playoffs, 15-minute overtime periods continue until a winner is determined. Overtime follows a three-minute intermission after the end of the regulation game. Prior to start of overtime, a coin flip is performed in which the captain of the visiting team calls the toss. The team that wins the coin flip has the option either to receive the kickoff or choose the side of the field they wish to defend. Ties are rare in the NFL; a game between the Minnesota Vikings and Green Bay Packers on September 16, 2018 ended in a 29–all draw. The previous occurrence was one week earlier, on September 9, 2018.