From TF2 Wiki
Overtime occurs when the timer runs out on a map with an objective currently being contested, and gives the attacking team a brief window to win the game with a last-second push. Onand maps when the timer runs out and a point has been partially captured. It ends either when the capture has been completely reverted (in which case the game will end) or the capture is completed (in which case more time is added to the timer and the game continues). On maps, overtime will occur if the cart is not moving backwards and the cart timer will automatically change to 5 seconds maximum. It ends when the timer runs out and no BLU players manage to secure it in time (ending the game), or if cart moves to a checkpoint (adding more time). On maps, Overtime is awarded if either teams is anywhere outside of it's spawn area, whether it's being carried by an enemy or dropped on the ground. The game will end once both teams Intelligence have returned to their base, either by being captured and returned, or defended until it returned on its own. During games, Overtime occurs when one team's counter has reached zero but the other team has partially captured the point. Overtime will continue as long as the point continues to be disputed, and can occur a second time if the second team captures the point and the first team disputes it again, resulting in the possibility of an unending game.
Overtime generally is fast and hectic, oftentimes with the entire offensive team rushing the objective in a desperate attempt to salvage their game, and the entire defensive team crowded around the contested objective.are a common Overtime tactic on control point and payload maps, and are often sent on suicide runs to keep intel alive until a full team can coordinate an attack to fully capture it.
- When King of the Hill mode was , the would repeatedly remind all players that it was "Overtime. Overtime! Overtime..." This was fixed by Valve on August 15th, 2009 bug fix, but remained an option for server admins due to popular reception by the TF2 community.