The influence of the allowed running time on the choice of the parameters of an ant system is investigated. It is shown that different parameter values appear to be optimal depending on the algorithm run-time. The performance of the MAX-MIN Ant System (MMAS) on the University Course Timetabling Problem (UCTP) — a type of constraint satisfaction problem — is used as an example. The parameters taken into consideration include the type of the local search used, and some typical parameters for MMAS — the τ _min and ρ. It is shown that the optimal parameters depend significantly on the time limits set. Conclusions summarizing the influence of time limits on parameter choice, and possible methods of making the parameter choice more independent from the time limits, are presented.