How long are U16 and U19 games?

Rule 6.1 of the Official Rules and Case Book says a regulation game should consist of:

• Four ten-minute periods of actual playing time (stop time) in the U16 and older age divisions at the AA level.
• Two twenty-minute periods in the U16 and older age divisions below the AA level.

If periods of that length are not possible (for example a late start), equal-length periods are played, and any extra ice time is added evenly to each period. Overtime is at the discretion of the tournament organizers or local governing body, with overtime periods the same length as regulation periods. Any penalty not expired at the end of regulation carries into overtime.