SWITCH DEVICE, VEHICLE-MOUNTED COMMUNICATION DEVICE, VEHICLE-MOUNTED COMMUNICATION SYSTEM, TIME CORRECTION METHOD, AND TIME CORRECTION PROGRAM

This switch device includes: a relay unit configured to perform a first relay process of relaying data between function units installed in a vehicle and belonging to different VLANs; a calculation unit configured to calculate time correction information on the basis of a transmission time of data from a first function unit serving as the function unit to the switch device, a reception time in the switch device of the data transmitted from the first function unit, a transmission time of data from a second function unit serving as the function unit to the switch device, and a reception time in the switch device of the data transmitted from the second function unit; and a notification unit configured to notify the second function unit of the time correction information calculated by the calculation unit.