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
NFL regular season matchups are determined according to a scheduling formula. Within a division, all four teams play fourteen out of their sixteen games against common opponents – two games (home and away) are played against the other three teams in the division, while one game is held against all the members of a division from the NFC and a division from the AFC as determined by a rotating cycle (three years for the conference the team is in, and four years in the conference they are not in). The other two games are intraconference games, determined by the standings of the previous year – for example, if a team finishes first in its division, it will play two other first-place teams in its conference, while a team that finishes last would play two other last-place teams in the conference. In total, each team plays sixteen games and has one bye week, where they do not play any games.