In an effort to speed up the pace of the game, in 1955, Major League Baseball announced a new rule that required a pitcher to deliver his pitch within 20 seconds of taking a pitching position.
By today’s rules, that time limit is down to twelve seconds:
When the bases are unoccupied, the pitcher shall deliver the ball to the batter within 12 seconds after he receives the ball. Each time the pitcher delays the game by violating this rule, the umpire shall call Ball. The 12-second timing starts when the pitcher is in possession of the ball and the batter is in the box, alert to the pitcher. The timing stops when the pitcher releases the ball.
The intent of this rule is to avoid unnecessary delays. The umpire shall insist that the catcher return the ball promptly to the pitcher, and that the pitcher take his position on the rubber promptly. Obvious delay by the pitcher should instantly be penalized by the umpire.
“2012 Edition: Official Baseball Rules.” MLB.com. Commissioner of Baseball, 2011. Web. Accessed 24 January 2014. http://mlb.mlb.com/mlb/downloads/y2012/Official_Baseball_Rules.pdf