In this tutorial, the folks at calomel.org show us how to get Chrony set up on FreeBSD. Chrony is an alternative setup of the Network Time Protocol. See the link below for full instructions.

Chrony is an accurate network time daemon and an alternate implementation of the Network Time Protocol (NTP) compared to ntp.org’s NTPd, Ntimed, OpenNTPd and systemd-timesyncd. Chrony can be used to sync with NTP servers, reference clocks (e.g. GPS receiver), and even input by hand for an air-gapped network. The daemon will operate as an NTPv4 (RFC 5905) server and peer providing time service to other computers in the network.

We will build Chrony from source on FreeBSD and the daemon will the configured to be a Network Time Protocol (NTP) server on the local LAN to provide millisecond accuracy to its local clock as well as to the hundreds of clients in the cluster.

Full tutorial: https://calomel.org/chrony_network_time.html