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 League
The NFL adopted some of the innovations introduced by the AFL immediately and a few others in the years following the merger. One was including the names on player jerseys. The older league also adopted the practice of using the stadium scoreboard clocks to keep track of the official game time, instead of just having a stopwatch used by the referee. The AFL played a 14-game schedule for its entire existence, starting in 1960. The NFL, which had played a 12-game schedule since 1947, changed to a 14-game schedule in 1961, a year after the American Football League instituted it. The AFL also introduced the two-point conversion to professional football thirty-four years before the NFL instituted it in 1994 (college football had adopted the two-point conversion in the late 1950s). All of these innovations pioneered by the AFL, including its more exciting style of play and colorful uniforms, have essentially made today's professional football more like the "AFL" than like the old-line NFL. The AFL's challenge to the NFL also laid the groundwork for the Super Bowl, which has become the standard for championship contests in the United States of America.