A method is based on a communication- and data network for the automatic time synchronization of field devices, namely fill-level measuring devices and pressure measuring devices as well as field-device control units. The method comprises the steps of: determining a current time value by the field device or by the field-device control unit, and providing a desired value in a central server. Furthermore, the method comprises the following steps: comparing the current time value with the desired value, and setting the current time value to the desired value when the desired value differs from the current time value by more than a predetermined threshold value.