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.
Penalty (gridiron football)
Moreover, the game clock will run once the ball is placed. If such a runoff occurs with 10 seconds or less remaining, the half automatically ends. Since the enforcement of the 10-second runoff, eight regular season NFL games ended automatically due to this rule: 2005 Arizona-St. Louis, 2009 Cincinnati-Green Bay, 2011 Chicago-Oakland, 2012 Washington-Philadelphia, 2012 New England-Arizona (which cost New England the chance to attempt a field goal at the end of the half in a game they eventually lost by two points), 2014 St. Louis-Tampa Bay (which cost Tampa Bay a chance to attempt a game-winning field goal), 2015 New England-New York Jets (which cost the Jets an attempt to throw a Hail Mary and force the game to overtime) and 2017 Atlanta-Detroit (which cost the Lions a chance to win the game). A pre-season game in 2006 between Houston and Kansas City had the first half end automatically due to an intentional grounding foul with less than 10 seconds left. A 2013 divisional playoff game between the New Orleans Saints and the Seattle Seahawks also ended on a 10-second runoff after Saints wide receiver Marques Colston threw an illegal forward pass.