ChronyControl

ChronyControl provides a straightforward means fo installing and monitoring chrony, which has now been ported to OS X.

The standard installation of OS X includes ntpd, probably the most widely used software for keeping a computer clock synchronised with other computers/clocks on the Internet. However, unless the Mac is online for extended periods of time, ntpd can be very slow to synchronise with other clocks, and the system time can be at wild variance with true time. The chrony software addresses the issues associated with ntpd. This is fully explained in the FAQ.
Files installed by ChronyControl: ChronyControl will install the chrony software and associated files on your Macintosh chronyd - /usr/local/bin chronyc - /usr/local/bin chronylogrotate.sh - /usr/local/bin chrony.conf - /etc/chrony.d/chrony.conf launchd plist - /Library/LaunchDaemons/org.tuxfamily.chronyd.plist launchd plist - /Library/LaunchDaemons/org.tuxfamily.chronyc.plist privileged helper - /Library/PrivilegedHelperTools/net.whatroute.chronycontrol
After installation you can also monitor and configure the chrony software from the command line, as you would on any other Unix system. The commands are documented at the chrony website.
Note: While the software is classified as free, it is actually donationware. Please consider making a donation to help support development.