Animals living in pairs often benefit from making behavioural switches synchronously. However, there is a trade-off between the need to synchronize and the need to stick to the individually different ideal time for the switch We model this situation, assuming two mechanisms for achieving synchronization: either to be ready before the ideal individual moment, or to wait beyond it. The model identifies an optimal com¬bination of readiness and waiting that brings the maximum benefit, in dependence on parameters includ¬ing relative costs of nonsynchrony, acting too early, and acting too late. The model is examined in two variants, without or with communication between the animals about their preparedness to synchronize For a majority of parameter values, the optimal strategy is to synchronize without communication (by just reacting to the other animal’s action) and be ready before the ideal time, but not to wait. This strategy leads to premature switches in pairs compared to single animals. Communication only pays off when commu¬nicating is cheap and acting late is cheaper than acting prematurely. In this situation, communication is coupled with a pure waiting strategy and results in delayed switches. The model shows that synchromza-tion is not symmetric in time which is a consequence of the inherent informational asymmetry of time.