The Major League Baseball (MLB) season schedule consists of 162 games for each of the 30 teams in the American League (AL) and National League (NL), played over approximately six months – a total of 2,430 games, plus the postseason. The regular season runs from late March/early April to late September/early October, followed by the postseason which can run to early November. The season begins with the official Opening Day, and, as of 2018, runs 26½ weeks through the last Sunday of September or first Sunday of October. One or more International Opener games may be scheduled outside the United States or Canada before the official Opening Day.[1][2] It is possible for a given team to play a maximum of 22 games in the postseason in a given year, provided the team is a wild card and advances to each of the Division Series, Championship Series, and World Series with each series going the distance (3 games in the Wild Card series, 5 games in the Division Series, 7 games each in the League Championship Series/World Series).
The regular season is constructed from series. Due to travel concerns and the sheer number of games, pairs of teams are never scheduled to play single games against each other (except in the instance of making up a postponed game, or, formerly, a one-game playoff to determine a postseason berth); instead they play games on several consecutive days in the same ballpark. Teams play one mid-week series and one weekend series per week. Depending on the length of the series, mid-week series games are usually scheduled between Monday and Thursday, while weekend games are scheduled between Thursday and Monday. Teams start and end their season on a weekend and play for 26½ weeks. Due to the mid-week all-star break in July, teams are scheduled to play 27 weekend series and 25 mid-week series for 52 total series (16 divisional series, 20 inter-divisional series, 16 inter-league series). A team's road games are usually grouped into a multi-series road trip; home series are grouped into homestands.
Beginning with the 2023 season, teams play a balanced schedule as follows: thirteen games are played against each of the other four teams in their own division (52 games total), six or seven games against each of the other ten teams in their own league (64 games total), four games against one "geographic rival" from the other league, and three games against each of the other fourteen teams from the other league, for 46 total interleague games. Under this schedule, divisional games consist of two, three or four-game series, intraleague games consist of three or four-game series, and the interleague games consist of two two-game series against the geographic rival (one series home and one away) and a single three-game series against the other interleague opponents (the home team alternating every year).
Note that rainouts and other cancellations are often rescheduled ad hoc during the season, sometimes as doubleheaders. However, if two teams are scheduled to meet for the final time in the last two weeks of the season, and the game is cancelled, it may not be rescheduled if there is no impact on the divisional or wild card races. For example, in 2016, the September 29 game between the Cleveland Indians and Detroit Tigers was originally cancelled due to rain. Because the teams were unable to reschedule a make-up date before the end of the season on October 2, and it did not affect the divisional race, the game was not rescheduled. In contrast, a 2008 AL Central division game between Detroit and the Chicago White Sox needed to be made up following the last day of the regular season because it played a part in the division race involving the White Sox and the Minnesota Twins.
From 1953 to 1981, Harry Simmons was responsible for devising the Major League Baseball schedule. Henry and Holly Stephenson, a husband-and-wife team, were in charge of constructing the MLB calendar for over two decades (1981–2004).[3][4][5] For the 2005 schedule, the MLB selected the Sports Scheduling Group, a small company located outside Pittsburgh, to craft the schedule for that year. Each year, the MLB considers the scheduling proposals from various external groups.