The NTP Daemon (ntpd), configured at Services > NTP, allows pfSense to act as a Network Time Protocol server for a network, and also keeps the clock in sync against remote NTP servers as an NTP client itself.
Before enabling this service, ensure that the router's clock keeps fairly accurate time.
The ntp.org NTPD distribution of ntpd is used.
By default the NTP server will bind to and act as an NTP server on all available IP addresses. This may be restricted using the Interface(s) selection on Services > NTP.
This service should not be exposed publicly. Ensure inbound rules on WANs do not allow connections from the Internet to reach the NTP server on the firewall.
If a serial GPS is present, it may be selected and used as a time source. Currently only NMEA format GPS output is used, other modes may work but require additional testing/hardware availability.