Page "Canadian football" Paragraph 52

The clock does not run during convert attempts in the last three minutes of a half.

If the 15 minutes of a quarter expire while the ball is live, the quarter is extended until the ball becomes dead.

If a quarter's time expires while the ball is dead, the quarter is extended for one more scrimmage.

A quarter cannot end while a penalty is pending: after the penalty yardage is applied, the quarter is extended one scrimmage.

Note that the non-penalized team has the option to decline any penalty it considers disadvantageous, so a losing team cannot indefinitely prolong a game by repeatedly committing infractions.