A communication system includes a plurality of sensor terminals each having an individual time and a management terminal having a reference time. The management terminal associates the individual time with the reference time at which the individual time was received and stores the associated times as a time pair. The management terminal determines a communication delay time using the configuration information of the hardware of the sensor terminal, the version of the software of the sensor terminal, the configuration information of the hardware of the management terminal, the version of the software of the management terminal, and a communication delay-causing combination table. The management terminal corrects the correspondence relationship between the individual time and the reference time in accordance with the communication delay time and corrects information detection time received from each of the plurality of the sensor terminals based on the corrected correspondence relationship.