How TF2 deals with the timelimit by default depends on the map type.
- Timelimit is completely ignored
- Map ends immediately if one team is ahead. If the teams are tied, ends in a stalemate or goes to Sudden Death depending on setting of mp_stalemate_enable
- Capture the Flag
- Symmetric Control Points (5CP)
- Map ends at the end of the round. In multi-stage maps, BLU only wins the round when they win the final stage.
- Attack/Defend Control Points
- PASS Time
- Player Destruction
- Robot Destruction
- Special Delivery (I think?)
- Map ends at the end of the current stage of a multi-stage map
- Payload Race (on all official maps anyway)
- Territorial Control
The cvar mp_stalemate_at_timelimit
can be used to make all maps use the CTF/5CP system.