A patient support apparatus includes a frame, patient support surface, clock, transceiver, and controller. The transceiver communicates with a headwall and/or a local area network. The controller detects the occurrence of an event and sends a message to a server in communication with the local area network in response to the event. The controller updates its estimate of the local time based upon time data received from the server. The controller may also and/or additionally receive first and second time updates from two different sources. When received, the controller updates its estimate of local time based upon at least one of the following: (a) a comparison of its estimate of local time with the time data from the first source; and (b) a comparison of its estimate of local time with the time data received from the second source.

A method for sensor operation includes deploying a network of sensors (22), which have respective clocks (36) that are not mutually synchronized. At least a group of the sensors receive respective signals emitted from each of a plurality of sources (24, 26), and record respective times of arrival of the signals at the sensors according to the respective clocks. Location information is provided, including respective sensor locations of the sensors. The respective clocks are synchronized based on the recorded times of arrival and on the location information. In the process the sources may be localized, or if the sources are far away, then their directions may be resolved. Sensor positions may also be resolved in the process.

[Problem] To provide a time synchronization mechanism that is not affected by link asymmetry between time synchronization devices. [Solution] A DC 4 used in a time transmission system that transmits and receives a PTP packet between a master node 1 and a slave node 2 via the DC 4 and synchronizes time of the slave node 2 based on time information on the transmission and reception includes a PTP clock unit 12 that synchronizes time information by the arrived PTP packet, a frequency clock unit 21 that synchronizes time information by a frequency signal, a delay setting unit 22 that sets, such that a transmission delay of the PTP packet between the master node 1 and the slave node 2 becomes a setting delay Lmax, a waiting time of the PTP packet based on a time difference between a departure time of the PTP packet and an arrival time of the PTP packet at the DC 4, which is determined from the time information of the frequency clock unit 21, and a time adjustment unit 26 that corrects a time shift from reference time in the time information of the frequency clock unit 21 based on the time information of the PTP clock unit 12.

Time information for various locations can be automatically generated for display on a portable electronic device. The time information can include time information for remote locations away from the current location of a user. The time information can be generated without requiring user input specifying the locations. The locations can be determined or identified based on context information of the user or context information of contacts of the user. The locations can be prioritized and the time information can be displayed according to the prioritization.