Method and apparatus for synchronizing the cycle time of several buses as well as corresponding bus system

A method for synchronization of at least two buses (103B1, 103B2), each having at least a first bus subscriber (101, 102, 105), wherein the buses are connected via at least one second bus subscriber (100) and for each bus a first or second bus subscriber acting as the time master and are present on the respective bus from the respective time master cycle times of the basic cycles, characterized in that in the at least two buses (103B1, 103B2) is determined in each case a global time, and from the global times of the buses, the discrepancies between the global times of the at least two buses (103B1, 103B2) are determined, which are interconnected via the at least one second bus subscriber (100), the function of the discrepancies between the global times to adapt the cycle times of the at least two buses (103B1, 103B2) to each of at least one as the time master in a bus acting first or second bus subscriber is effected so that the at least two buses (103B1, 103B2) are synchronized with respect to the cycle times.