National Football League regular season

The National Football League regular season begins the weekend after Labor Day. Each team plays 16 games during a 17-week period. Traditionally, the majority of each week's games are played on Sunday afternoon, with weekly games on Sunday night and Monday night, and occasional games on Thursday night or Saturday.

Game times
Currently, the majority of NFL regular-season games are played on Sundays at 1 pm or 4:15 pm ET, with 4:15 pm games usually going to games hosted in the Pacific Time Zone or Mountain Time Zone. The current NFL television contract awards the American broadcast of these games to FOX or CBS, with FOX showing games where the visiting team is from the NFC and CBS showing games where the visiting team is from the AFC. The schedule allows for 4 other regular time slots:
 * 1) One Sunday night game, which has been regularly scheduled since 1987 and currently appears on NBC.
 * 2) One Monday Night Football game, which has been regularly scheduled since 1970 and currently appears on ESPN.
 * 3) For the last few weeks of the regular season (after the NCAA football regular season has concluded), multiple Saturday games, which usually appear on the NFL Network following the usual Sunday system.
 * 4) On Thursday nights since 2006, one game has been played and aired on the NFL Network on the weeks including and after Thanksgiving Day.  In addition, during the day on Thanksgiving, the NFL has played Thanksgiving Classic games since 1920; by tradition the Dallas Cowboys and the Detroit Lions always host these afternoon games.

History
In its early years after 1920, the NFL did not have a set schedule, and teams played as few as eight and as many as sixteen games, many against independent professional, college or amateur teams. From 1926 through 1946, they played from eleven to fifteen games per season, depending on the number of teams in the league. From 1947 through 1960, each NFL team played 12 games per season. In 1960, the American Football League began play and introduced a balanced schedule of 14 games per team over a fifteen week season, in which each of the eight teams played each of the other teams twice, with one bye week. Competition from the new league caused the NFL to expand and follow suit with a fourteen-game schedule in 1961. From 1961 through 1977, the NFL schedule consisted of fourteen regular season games played over fourteen weeks. Opening weekend typically was the weekend after Labor Day, or even two weekends after Labor Day. Teams played six, or even seven exhibition games. In 1978, the league changed the schedule to include sixteen regular season games and four exhibition games. From 1978-1989, the sixteen games were played over sixteen weeks.

In 1990, the NFL introduced a bye week to the schedule. Each team played sixteen regular season games over seventeen (eighteen in 1993 and 2001) weeks. During the season, on a rotating basis, each team would have the weekend off. As a result, opening weekend was moved up to Labor Day weekend. (The league had an odd number of teams (31) from 1999 to 2001. During that period, at least one team had to be given a bye on any given week.)

Since the 2002 season, the league has scheduled a nationally televised regular season kickoff game on the Thursday night after Labor Day, prior to the first Sunday of NFL games to kick off the season. The first one, featuring the San Francisco 49ers and the New York Giants, was held on September 5, 2002 largely to celebrate New York City's resilience in the wake of the September 11, 2001 attacks. Since 2004, the NFL has indicated that the opening game will normally be hosted by the defending Super Bowl champions as the official start of their title defense. Thus, under this scheduling system, the earliest the regular season could begin is September 4, as it was in the 2008 season, due to the 1st falls on a Monday, while the latest possible is September 10, as it was in the 2009 season, due to the 1st falling on a Tuesday.

Formula


Currently, each team's 16-game regular season schedule is set using a pre-determined formula:


 * Each team plays the other three teams in their division twice: once at home, and once on the road (six games).
 * Each team plays the four teams from another division within its own conference once on a rotating three-year cycle: two at home, and two on the road (four games).
 * Each team plays the four teams from a division in the other conference once on a rotating four-year cycle: two at home, and two on the road (four games).
 * Each team plays once against the other teams in its conference that finished in the same place in their own divisions as themselves in the previous season, not counting the division they were already scheduled to play: one at home, one on the road (two games).

This schedule guarantees that all teams will play each other at least once every four years. Ideally, it also secures alternating home and away games, but in some instances this goal has been set aside for other scheduling priorities (for example the Seahawks played both at Cleveland and at Pittsburgh in 2007 and will be on the road against both teams again in 2011 (as well as being at home against Cincinnati and Baltimore both years as well).  This schedule also guarantees that regardless of a given team's final divisional placement in the previous season, the 16 games that team plays in this current season will consist of:


 * four games against opponents who finished the previous season in first place in their respective divisions,
 * four games against opponents who finished the previous season in second place in their respective divisions,
 * four games against opponents who finished the previous season in third place in their respective divisions, and
 * four games against opponents who finished the previous season in fourth place in their respective divisions.

For example, in the 2009 schedule grid shown above and to the right, the Browns finished fourth in their division in the previous (2008) season. Thus, in the 2009 season, they played four games against first-place teams (Steelers twice, Chargers, Vikings), four games against second-place teams (Ravens twice, Broncos, Bears), four games against third-place teams (Bengals twice, Raiders, Packers), and four games against fourth-place teams (Bills, Jaguars, Chiefs, Lions).

Prior to 2002 (when the league expanded to 32 teams) the league used similar scheduling rubrics, though they were adjusted for the number of teams and divisions. From 1970 to 1994, and again from 1999 to 2001, the league did not have equal numbers of teams in every division, which allowed for unbalanced schedules. The only time since the merger that the league has been completely "balanced" has been from 1995 to 1998 (with 6 divisions of 5 teams each) and since 2002 (with 8 divisions of 4 teams each). Additionally, prior to 2002, teams always played four of the teams from a division in the other conference on a rotating basis, but not their own; meaning that while an AFC team would be more likely to play each NFC team on a regular basis, they could go far longer without playing every team in their own conference. For example, between 1970 (when the leagues merged) and 2002 (when the current schedule was introduced) the Denver Broncos and the Miami Dolphins played only 6 times; including a stretch (1976–1997) where they met only once in 22 seasons. Under the current system, they are guaranteed to meet at least every third year.

After the 2009 season, after all of the teams have cycled through playing against each other both home and away, the league will then implement a modified version of the 2002 scheduling formula, tweaked especially to relieve East Coast teams from having to travel to the West Coast multiple times during the same season. Under the original 2002 formula, those teams scheduled to play all the AFC West clubs had to travel to both Oakland and San Diego in the same season, while those clubs playing the NFC West had to make their way to both San Francisco and Seattle. In the 2008 season, the New England Patriots and New York Jets each had to make cross-country trips to all four of the aforementioned West Coast teams. Under the 2010 modified formula, clubs would only have to visit one West Coast team (AFC West or NFC West), plus one western team from the same division closer to the Midwest. Specifically, those clubs traveling to Oakland would then instead play at Denver, while those playing at San Diego would instead just have a shorter trip to Kansas City. For those playing NFC West teams, some will travel to both San Francisco and Arizona in the same season, while others will instead make trips to Seattle and St. Louis.

There also have been proposals to expand the regular season schedule to 17 or 18 games per team. Current Commissioner Roger Goodell has said he favors expanding it to 18 games. However, he said that a longer regular season is unlikely to begin any earlier than 2011, due to the requirement that the NFL Players Association must approve the change. One of the proposals for the 17th and 18th games is to have every team play at least one game abroad every year. Another idea being put forth by Houston Texans owner Bob McNair is to move the traditional regional rivalries that are currently played in the preseason (such as the Governor's Cups) into a permanent annual part of each NFL team's schedule. The NFL Players' Association opposes extending the season, largely because of injury concerns, and extending the season would require that such an extension be included in the next collective bargaining agreement, which expires in 2011.

Future scheduling rotation
For the next 4 years, assuming no major rules changes and no canceled seasons:

Regular season games played outside of the U.S.
To date, several NFL regular season games have been played outside of the U.S. The first was the 2005 game between the Arizona Cardinals and the San Francisco 49ers, which was played in Mexico City.

In October 2006, NFL club owners approved a plan to stage up to two international regular season games per season beginning in 2007 and continuing through at least 2011. The New York Giants and the Miami Dolphins  played at Wembley Stadium in London on October 28, 2007 for the first of these games. A second game in London took place on Sunday 26 October 2008, when the San Diego Chargers took on the nominal 'home team' New Orleans Saints, also at Wembley. The New England Patriots were the designated visitors when they beat the Tampa Bay Buccaneers 35-7 on October 25, 2009.

The long term plan is to have two international games played every year, on a 16-year rotating schedule that would guarantee that each team would get to play twice over that span: once as the home team and once as the away team.

The Buffalo Bills will play eight games through 2012 in Toronto, Ontario as part of the Bills Toronto Series. The Bills will play five regular season games (one each season) and three preseason games (one every other season) through 2012 in the Rogers Centre. The Bills first of eight games in Toronto was a preseason game against the Pittsburgh Steelers on August 14, 2008. The Dolphins beat the Bills 16-3 in the first regular season game of the series, on December 7, 2008. The New York Jets played the Bills on Thursday, December 3, 2009.

Disruptions of the schedule
From the beginnings of the NFL, most teams shared stadiums with Major League Baseball teams with the MLB teams holding leases giving them priority. The NFL was required to schedule around September baseball games. In October this frequently resulted in NFL teams having to reschedule on short notice if the MLB team in their city made the playoffs. Sometimes the NFL game could be moved to Saturday or Monday. The NFL would often schedule October division games so that teams would be able to swap home game dates if it appeared that the MLB playoff schedule would make a stadium unavailable to the NFL. Probably the worst case was in 1973 when the New York Jets played at Shea Stadium and were forced to play their first six games on the road because the Mets were in the World Series. Currently, only two NFL teams share their home stadium with a baseball team: the Miami Dolphins share Sun Life Stadium with the Florida Marlins, who will start playing in a new baseball stadium, Miami Ballpark, in 2012, and the Oakland Raiders share the Oakland-Alameda County Coliseum with the Oakland Athletics. (Also, the Buffalo Bills host one game a year at the Rogers Centre which is the home of the Toronto Blue Jays; this is only an issue in the preseason, since all regular season games to date have been scheduled after the end of the MLB regular season, and the Blue Jays have not made the MLB playoffs since 1993.)

In 2001, Week 2 of the season was canceled because of the September 11, 2001 terrorist attacks. Week 2's games were made up by adding an 18th week to what was originally a 17-week schedule. The games were played on Sunday, January 6 and Monday, January 7, 2002. The post-season schedule was moved back a week, including Super Bowl XXXVI due to the lack of a bye week before the game.

The American Football League, the precursor to today's American Football Conference, postponed Week 12 of the 1963 season because of the assassination of President Kennedy, which took place on Friday, November 22. The AFL's games were made up by adding a 15th week to a 14-week schedule. The older and more established National Football League went ahead and played as scheduled on Sunday, November 24, 1963.

A few days before the start of the 2005 NFL Season, the Louisiana Superdome was severely damaged by Hurricane Katrina, and much of the city of New Orleans was destroyed. The New Orleans Saints' eight scheduled home games were moved to other locations, including Giants Stadium, the Alamodome in San Antonio, and Louisiana State University.

On September 14, 2008, the Houston Texans were scheduled to host the Baltimore Ravens. The game was postponed till November 9 because of Hurricane Ike (which caused some damage to Reliant Stadium) and several other changes had to be made to the schedule.

The roof of the Hubert H. Humphrey Metrodome collapsed on December 12, 2010, resulting in the stadium being unusable for the remainder of the regular season. The last two of the Minnesota Vikings' home games had to be moved: one to Ford Field in Detroit (which also led to the game being postponed the following Monday night) and another to TCF Bank Stadium, the University of Minnesota's college football stadium.

In August 1995, the Oakland Raiders moved back from Los Angeles after the preseason schedule had already begun. Aside from moving the Raiders home games to Oakland, no last-minute changes were needed.

The 1982 and 1987 seasons were both shortened by labor disputes. The 1982 strike lasted 57 days. Weeks 3 through 10 were canceled, but an additional week was added to make a 9-game schedule. The 1982 playoff matchups were determined by conference standings only. The 1987 strike and subsequent lockout lasted 24 days but only one week of the schedule was lost. Weeks 4 through 6 were played with replacement players. The rest of the season was played as originally scheduled, for a total of 15 games per team.

In the event of the 2011 NFL season being disrupted because of an ongoing labor dispute, the NFL has arranged its schedule to facilitate easier cancellations and postponements. In addition to an emergency scenario of an eight-game schedule beginning in late November, the NFL also arranged its full-length schedule such that weeks 2 and 4 have no division games, week 17 has all division games, and all week 3 matchups can be moved into each team's respective bye week. The league also has a contingency plan to postpone Super Bowl XLVI one week, which (assuming a full playoff schedule) would allow a 13-game schedule with five division games for each team to be played beginning as late as October 16.