This location information providing system includes at least one message transmitter and an authentication server which respectively have times synchronized with each other. The message transmitter includes: a generation means for generating an authentication code to be dependent on the time and a unique code; and a...

Provided is a system with which time synchronization can be realized for a plurality of devices that are disposed at positions where a GNSS signal cannot be received. A time synchronization system comprises: a reference time acquisition unit that acquires, on the basis of a wireless signal from a positioning satelli...