Q&A: Drifting time

Q Our Macs are connected to a network which has Internet access here in Mauritius. Although we configured them to set their times and dates automatically, and they did all synchronise to the same time, they have since drifted apart, and now show quite different times. How can we bring them back to keep to the same time?

A Normally configuring the Date & Time tab in the Date & Time pane to set times automatically should ensure that each connects to a Network Time Protocol (NTP) server and synchronises with it. Once that has happened, they will each re-synchronise periodically, and should stay within a very few seconds of one another.

Before pursuing any other issues, go round and check that each of the Macs is still so configured, and that they are set to use the same server, in your case Apple Asia. Sometimes users may fiddle with this setting, and might have turned it off, or chosen a different server.

Synchronisation can also be lost if the Macs cannot access the designated server, which does not need to be one of Apple’s. If you have intermittent problems resolving IP addresses from names, you can substitute an equivalent IP address, perhaps. Contact your local university’s computer science department and ask them if they run a time server that is accessible over the Internet: this is likely to shorten the time delay involved in synchronisation and will make it more reliable.

If the worst comes to the worst, you can run your own local time server, but the potentially expensive part is acquiring a suitably accurate clock. The cheapest way would be to have a dedicated Linux server with a GPS-based clock, sitting on your own network, but you will probably be able to find someone else already doing that nearby.

Comments There is further information about NTP here.

Updated from the original, which was first published in MacUser volume 27 issue 1, 2011.