Mac OSX is configured out of the box to automatically synchronize with a time server, so no further activities are required.

However, for being 100% sure you can validate if the automatic time synchronization is still enabled:

1. Click on the Apple Menu in the upper left-hand corner of your screen and select “System Preferences.”
2. Select the Date and Time Icon.
3. Click on the “Date and Time” icon in the Preferences Panel to activate the “Date and Time” preferences.
4. Assure that the “Set date & time automatically” checkbox is checked.