  At the Belle II experiment a Time-of-Propagation (TOP) counter is used for
particle identification in the barrel region. This novel type of particle
identification device combines the Cherenkov ring imaging technique with the
time-of-flight and therefore it relies on a precise knowledge of the time of
collision in each triggered event. We discuss the performance of the counter
and present a maximum likelihood based method for the determination of event
collision time from the measured data.
