Set the System Time in Mac OS X from the Command Line
The clock in Mac OS X sets itself automatically by default, but if you want to set the precise time or are looking for a command line solution to set system time, you can do so with a tool called ntpdate, or the standard ‘date’ command.
Set System Date in Mac OS X from Command Line with a Central Time Server
For ntpdate, which sets the date and time based on the time from a central server accessed via the internet, you’d want to point it either at Apple’s time servers or pool.ntp.org as follows to get the exact time:
sudo ntpdate -u time.apple.com
Enter the admin password when asked, and you’ll soon see something like the following:
4 Jul 14:30:11 ntpdate: adjust time server 126.96.36.199 offset 0.000336 sec
The offset at the end lets you know how divergent the system clock was with the newly set time. In this example, the system clock was off by a laughably small fraction of a second.
You generally don’t need to do this if you use the “Set date and time automatically” feature within the Date & Time system preferences, though by setting clocks through the command line you could be sure that each machine on a network shows the exact same time.
Set the Mac System Date Manually by Terminal Command
Another approach is to set the date manually from the command line by using the “date” command string, where date is in the [mm][dd]HH]MM[yy] format, which is Month Date Hour Minute Year without any separation. This looks something like:
For that example, it would set the date as “July 12 2018 at 12:23″.
You can learn more about setting the date with date –help, which also specifies that you can even set the seconds if you want to.
The ‘date’ trick is what you’d want to use if the Mac in question does not have internet access for one reason or another.
Topmost image taken from the Flipclock screensaver