PURPOSE: To synchronize the local time of a network node with the standard time. CONSTITUTION: A burst of a synchronizing message carrying a standard time stamp is sent according to a scheduled protocol. Each node receives the synchronizing message and time-stamps it to obtain pieces of time data based upon a 1st time scale and a 2nd time scale. The scheduled protocol prescribes tentative relation among those pieces of time data. According to the scheduled protocol, each node determines a difference between 1st time based upon one time scale and time relating to 2nd time and 3rd time based upon the other time scale. Then the node updates its local time according to the difference. The node maintains a global precision value for estimating a synchronism error. When the global precision value exceeds various thresholds, the node requests resynchronization or ends the synchronizing message according to its internal time.