Data receiving apparatus, data transmission apparatus and data transmission system

According an aspect of the present invention, a data receiving apparatus includes a calculator. The calculator (1) stores a date and time indicated by the clock unit in association with a first local date and time in the memory as a reference date and time, when the packet includes first date-and-time data indicating the first local date and time and information indicating that the first date-and-time data can be used for date and time association, and (2) calculates, when the packet includes sensor data and second date-and-time data indicating a second local date and time associated with the sensor data, a third date and time based on a difference between the first local date and time and the second local date and time, and on the reference date and time.