I'm not aware of any such cvar. The round time is usually determined by the map maker.
The problem with having a round time cvar and/or plugin is that different game types would need different round times:
- Attack/Defend CP, Medieval CP, and PL start with fixed time and it's extended by a specific amount of time every time a point in capped. RED wins when this time runs out.
- 5CP starts with fixed time and it's set back to that time every time a point is capped. Game stalemates if teams are tied when time runs out.
- TC starts with a fixed time. Game stalemates if teams are tied when time runs out.
- CTF lasts for the entire map time or until X captures are made (configureable by cvar; defaults to 3). Game stalemates if teams are tied when time runs out.
- KOTH lasts forever until the point is capped for the first time, at which point it can be between 3 and 6 minutes unless the attacking team managed to keep the point in play during overtime.
- PLR lasts forever (except on plr_nightfall) until one team pushes their cart all the way to the end. plr_nightfall starts the carts automatically rolling forward when time runs out.
- Arena lasts forever until one team is dead or the point is captured.
In other words: CTF, PLR, and Arena are the only two types that really need a round timer... and maybe KOTH with really bad teams.
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