A method for establishing a global time base in a time-controlled communications system comprising a network and multiple subscribers connected to it. At least one of the subscribers of the communications system is defined as a time master with which the remaining subscribers are synchronized. In order to allow for a synchronization of the communications system that is on the one hand as simple as possible and realizable at low cost and on the other hand is secure and reliable, the present invention provides for one subscriber to be defined as the main time master and at least one further subscriber to be defined as a reserve time master. The order of the reserve time masters is predefined in the event that more than one subscriber is defined as a reserve time master. First an attempt is made to synchronize all subscribers of the communications system with the main time master. If this fails, then in each case the next reserve time master in the predefined order is selected and the attempt is made to synchronize all subscribers of the communications system with the selected reserve time master until either the synchronization of the subscribers of the communications system is successful or a synchronization of the subscribers with the last reserve time master fails as well.