OpenNTPD

OpenNPTD - Lightweight NTP server ported from OpenBSD

Emerge
Install OpenNTPD:

Service
Start the ntpd daemon:

Add the ntp daemon to the default runlevel:

Configuration
Default configuration file for openntd:

For further information read

systemd / timedatectl
systemd comes with timedatectl to manage your system clock time.

The manpage of timedatectl shows how ntpd and timedatectl can work together:

However, it also seems to work if ntpd.service is enabled (DEPRECATED, please use systemd-timesyncd instead as described below)

The time is synced despite the fact that timedatectl says ntp sync is off:

But in systemd 213 new feature arrived - systemd-timesyncd. It's a built-in NTP client designed as a part of systemd-networkd, and the recommended way to sync time with systemd.

External resources

 * http://www.openntpd.org/