Periods and overtime in ice hockey
A game consists of three periods of twenty minutes each, the clock running only when the puck is in play. In international play the teams change ends for the second period, again for the third period, and again after ten minutes of the third period, In North American play the last change is omitted.
Various procedures are used if a game is tied. In tournament play North Americans favour sudden death overtime, in which the teams continue to play until a goal is scored. International play uses an overtime period followed by a shoot-out if the score remains tied after the extra period; the shootout consists of five players from each team taking penalty shots against the other team's goaltender until one team has the preponderance of successful shots.