Scheduling algorithms are usually based on the assumption that we know
the exact durations $d_i$ of all the tasks that we want to schedule.
In real life, the durations $d_i$ may vary. In rare cases when we know
the probabilities of different durations, we can apply stochastic
scheduling methods. Most often, however, we do not know the
probabilities, we only know the upper bound $d^+_i$ and the lower
bound $d^-_i$ for the duration $d_i$; in other words, we know an *
interval* $[d^-_i,d^+_i]$ of possible values of duration $d_i$. In
these situations, we want a schedule that satisfies the given
constraints for all possible values of durations $d_i$ from the given
intervals. An algorithm for producing such a schedule is given in this
paper. As an example, this algorithm is applied to a railway station.