Comparison of American football and rugby union
A rugby union game is divided into two halves of 40 minutes (or shorter for lower-grade games, and breaks given halfway through each half if playing conditions are considered to be extreme) separated by a half time period of up to 15 minutes in an international match. Most notably, a rugby union game will continue after the scheduled end of a half (half-time or full-time) until the ball becomes dead - any occurrence that would have play restart with a scrum or lineout, or when a team scores. This has led to some "nail-biting" finishes where teams losing by only a small margin work their way towards scoring, and games can go on several minutes over time. Something similar can occur at the end of either half in American football, though usually for only a few seconds of additional time, because a play that begins before the half expires continues until the ball is dead regardless of whether there is any time left on the clock. In both sports, the clock is also stopped during substitutions and for injuries, so the referee does not need to add stoppage time as is done in soccer/Association football. American football games are made up of four quarters of 15 minutes each (less at the high school and youth levels), but the clock stops and starts according to specific rules, so that a 15-minute quarter lasts much longer.
Modern history of American football
The CFP system is centered on six major bowl games played on or near New Year's Day, often called the "New Year's Six". Three pairs of games rotate annually as hosts of CFP semifinals. The champions of the so-called Power Five conferences (ACC, Big Ten, Big 12, Pac-12, SEC) all receive guaranteed berths in one of the New Year's Six games, though not necessarily in the CFP semifinals. Notre Dame, a football independent but otherwise an ACC member, has its own arrangement for access to the New Year's Six should it meet specified criteria. A selection committee similar to those used by the NCAA basketball tournaments for men and women releases a weekly ranking concurrently with the AP Poll starting with the Monday after Week 10 of the season. After the completion of the regular season, the committee selects the four teams that will compete in the CFP semifinals and the at-large entries to the New Year's Six games. One of the at-large entries is reserved for the top-ranking champion of the so-called "Group of Five" conferences (American, Conference USA, MAC, Mountain West, Sun Belt). The semifinal winners advance to the College Football Playoff National Championship game. The first season of the new system was not without controversy, however, after TCU and Baylor (each with only one loss) both failed to receive the support of the College Football Playoff selection committee.