A method for adjusting a clock on board a motor vehicle, the clock providing an actual time for functions of the vehicle, the vehicle connected via wireless communication to a data server, the method including: the server transmitting a sequence of consecutive actual-time values, separated from one another by a fixed time interval; the vehicle receiving the actual-time values shifted by an unknown and variable time of flight between transmission and reception; for each received actual-time value: calculating a difference between an actual-time value received at a given instant and an actual-time value received at a previous instant; calculating a discrepancy between the calculated difference and the fixed time interval; calculating a cumulative disparity, consisting in summing the discrepancy calculated for a time value received at one instant and a time value received at the previous instant; determining the actual time for adjusting the on-board clock according to the disparity.

A communication device includes a first clock, a communication unit, a delay time acquiring unit, a selection unit, and a correction unit. The communication unit is configured to receive first packets from an outside communication device including a second clock and transmit second packets to the outside communication device. The delay time acquiring unit is configured to a first delay time and a second delay time. The selection unit is configured to select one of the first packet and the second packet as a target packet. The correction unit is configured to calculate a correction value based on a first minimum delay time or a second minimum delay time, and correct the delay time of the target packet using the correction value.

An object of the present invention is to provide a communication system and a communication method that can avoid network congestion using a simple approach. The communication system of the present invention is characterized in that a time distribution server that transmits time information to terminals distributes a time different from the standard time for each terminal, and the terminal performs communication on the basis of the distributed time, and further characterized in that, for a time synchronizing packet transmitted from a time distribution server on the Internet to a terminal, a node or the like in the middle of the path performs transfer control or rewrites the packet, thereby causing the terminal to recognize a different time, and the terminal performs communication on the basis of the time.

[Problem] An object is to obtain a time quality of another GM with high accuracy on the basis of a GM a time quality of which is known already. [Solution] A first TC 20 includes a time comparison unit 23 that calculates time difference information by comparing first time information of a first PTP processing unit 12 and second time information of a second PTP processing unit 22 with each other. In addition, a quality calculation device 5 measures time difference information until time difference information obtained by a time comparison unit 23 of the first TC 20 and time difference information obtained by a time comparison unit 43 of a second TC 40 match each other, and obtains a GM time quality of a second GM 30 on the basis of a transmission time error of the time transmission network 2 at a timing when both of pieces of the time difference information match each other.

A satellite radio-controlled watch, including a receiving unit for receiving a satellite radio wave containing time information and position information; a storage unit for storing intersection point information indicating a position of an intersection point between a reference line along a great circle orthogonal to a specific great circle on the earth or a reference line along the specific great circle on the earth or a circle parallel to the great circle and a time zone boundary, and time difference division information on a wedge-shaped or belt-shaped area that is adjacent to the reference line and to which the intersection point belongs, and a time zone determination unit for determining a time zone, based on the position information, the intersection point information, and the time difference division information.

A satellite radio-controlled watch, including a receiving unit for receiving a satellite radio wave containing time information and position information; a storage unit for storing intersection point information indicating a position of an intersection point between a reference line along a great circle orthogonal to a specific great circle on the earth or a reference line along the specific great circle on the earth or a circle parallel to the great circle and a time zone boundary, and time difference division information on a wedge-shaped or belt-shaped area that is adjacent to the reference line and to which the intersection point belongs, and a time zone determination unit for determining a time zone, based on the position information, the intersection point information, and the time difference division information.

A time synchronization method that is capable of selecting whether synchronization, by a timepiece unit that generates a time signal synchronized with a standard time and outputs it to an exterior, with the time is performed by time information obtained by receiving a radio wave including information relating to the time, or is performed by means of a holdover performed using a clock signal from an internal or external clock source. A schedule having a first time period in which the above-mentioned time information is used, and a second time period by means of the holdover is determined according to temporal reception characteristics of the radio wave at a reception location of the radio wave, and according to the schedule, supplying the timepiece unit with the time information or supplying the timepiece unit with the clock signal from the internal or external clock source.

A time synchronization method that is capable of selecting whether synchronization, by a timepiece unit that generates a time signal synchronized with a standard time and outputs it to an exterior, with the time is performed by time information obtained by receiving a radio wave including information relating to the time, or is performed by means of a holdover performed using a clock signal from an internal or external clock source. A schedule having a first time period in which the above-mentioned time information is used, and a second time period by means of the holdover is determined according to temporal reception characteristics of the radio wave at a reception location of the radio wave, and according to the schedule, supplying the timepiece unit with the time information or supplying the timepiece unit with the clock signal from the internal or external clock source.

The present technology relates to a data processing apparatus and a data processing method that enable correct clock synchronization by use of clock information. The data processing apparatus receives a digital broadcast signal so as to process content included in the digital broadcast signal and clock information also included therein for use in presentation synchronization on the content and sends via a transmission path the processed content and clock information to another data processing apparatus that presents the received content. On the other hand, the another data processing apparatus receives via the transmission path the content and clock information sent from the data processing apparatus so as to process presentation synchronization on the received content on the basis of the received clock information. The present technology is applicable to data processing apparatuses configured to process content, for example.

The present technology relates to a data processing apparatus and a data processing method that enable correct clock synchronization by use of clock information. The data processing apparatus receives a digital broadcast signal so as to process content included in the digital broadcast signal and clock information also included therein for use in presentation synchronization on the content and sends via a transmission path the processed content and clock information to another data processing apparatus that presents the received content. On the other hand, the another data processing apparatus receives via the transmission path the content and clock information sent from the data processing apparatus so as to process presentation synchronization on the received content on the basis of the received clock information. The present technology is applicable to data processing apparatuses configured to process content, for example.