ntpd

Start the daemon

$ sudo ntpd

$ sudo ntpd --quit

$ sudo ntpd --panicgate --quit

ntpd [options]

ntpd is the Network Time Protocol daemon that synchronizes the system clock with remote NTP servers or local reference clocks. It maintains accurate time by continuously adjusting the clock rate to compensate for drift.
The daemon reads its configuration from /etc/ntp.conf, which specifies time servers, access restrictions, and behavior options. Once running, it gradually slews the clock to avoid abrupt time jumps that could confuse applications.
For one-time synchronization without running a continuous daemon, use the --quit option. The --panicgate option allows initial sync even when the clock is far off.

-q, --quit

Set the time once and exit

Allow large time corrections (normally refused if >1000 seconds off)

Run in foreground, don't daemonize

Use alternate configuration file

Specify PID file location

Increase debug verbosity (can be repeated)

Large time jumps (>1000 seconds) are refused by default; use --panicgate for initial sync of badly drifted clocks. Conflicts with other time sync daemons (systemd-timesyncd, chrony). Port 123 (UDP) must be accessible. Modern systems often prefer chrony or systemd-timesyncd.

NTP was developed by David L. Mills at the University of Delaware, first appearing in 1985. The reference implementation ntpd has been the standard NTP daemon for decades.

ntpq(8), ntpdate(8), chrony(8), timedatectl(1)