It is possible to get 15 mins of race, seen it once on R2R server. Unfortunately after some requests i still havent found solution myself, i'd like to know the command aswell
You can only set times for races in hour increments using the command /hour=xx
You can use Airio to get timed races of non-whole hour increments - it does it I think by timing the number of minutes you want [e.g 15 mins], then sets /laps=xx where xx is the lap number the leader is on at the time when the 15 mins expires.