From BR Bullpen
When a game is tied after regulation play, sometimes seven innings in the minor leagues, but always nine innings in the major leagues, the game will go into extra innings.
In extra innings, the game continues as usual until the away team has scored more runs and the home team has completed a turn at bat, or the home team has scored more runs thus ending any chance for the away team to come back.
Before the advent of lights, extra inning games were often terminated and called a tie due to darkness. When lights were added to Wrigley Field in 1988, ties due to darkness were eliminated in the major leagues.
The most extra innings played in professional baseball is 24 by Rochester at Pawtucket in the International League on April 18, 1981. The record in the major leagues is 18 on May 1, 1920 between Brooklyn and Boston at Braves Field. The game was called a tie due to darkness.
In Nippon Pro Baseball, teams play three extra innings. If a team has not won after twelve innings the game is declared a tie. The exception is in the Japan Series and playoffs, where the game is played until it is decided conclusively. In the Korea Baseball Organization, the limit is also 3 extra innings, even in the Korean Series, resulting in occasional ties in the most important matches of the year.
In both the spring and summer Koshien Tournaments, games will last a maximum of 15 innings. If the score is still tied, the game will end in a tie and be replayed the next day.
In the 2008 World Junior Championship and 2008 Olympics, the IBAF introduced a new twist for the play of extra innings for that competition. If the game is still tied after the 10th inning, both teams will then start the 11th inning with two runners on base - occupying first and second base. The manager is free to chose any players in the line-up as his runners, as long as they bat consecutively. The player following the two runners in the batting order then leads off the inning at the plate. If a 12th inning is required, the batter whose turn is due comes to the plate to lead off as scheduled, and the two batters that precede him in the line-up start the inning on base, the batter before him on first base, and the batter before that on 2nd. For example, if the 4th hitter was the last to bat in the 11th inning, the 12th inning will start with the 3rd hitter on second base, the 4th hitter on first base, and the 5th hitter at the plate. The objective is to encourage the scoring of runs in extra innings in order to bring the game to a quick conclusion. This controversial rule has since been adopted in the Hoofdklasse and Cuban Serie Nacional. The rule was dubbed the "Schiller Rule" by American writer Peter Bjarkman in honor of former IBAF president Harvey Schiller, and the name has become commonly used in Cuba.
 Further Reading
- Philip J. Lowry: Baseball's Longest Games: A Comprehensive Worldwide Record Book, McFarland, Jefferson, NC, 2010.