Date and Time

The device's internal clock (date and time) can be set using one of the following methods:

Manually (see Configuring Date and Time Manually)
Automatically synchronized using a third-party, remote Simple Network Time Protocol (SNTP) server (see Synchronizing Date and Time through SNTP)
Automatically synchronized using the SIP Date header (see Synchronizing Date and Time through SIP)

For automatic synchronization, NTP takes highest preference, and then SIP Date header. For example, if you enable NTP, the device ignores the SIP Date header settings. If you do enable multiple synchronization methods, the device sends the SNMP alarm acClockConfigurationAlarm to notify you of this configuration scenario.