macOS Sierra: Set the date and time on your Mac
You can have the date and time set automatically using a network time server, or set your computer’s date and time manually. Be sure your time is correct so time stamps on emails, messages, and files are correct.
Choose Apple menu > System Preferences, then click Date & Time.
Click Date & Time, then set the date and time automatically or manually.
Automatically: Select “Set date and time automatically,” then choose the network time server for your region.
Manually: Deselect “Set date and time automatically,” click today’s date on the calendar, drag the clock’s hands to show the correct time (or enter the time), then click Save.
Click Time Zone, then set the time zone automatically or manually.
Automatically: Select “Set time zone automatically using current location.”
Manually: Deselect “Set time zone automatically using current location,” click a location on the map, click the Closest City pop-up menu, then choose the city closest to your location.
Show date and time in menu bar: Select the checkbox to see the date and time in the top-left corner of the menu bar. In “Time options” and “Date options,” set how you want the date and time to appear.
Announce the time: Select the checkbox to hear the time announced, then choose when you want it announced. If you want, you can customize the voice.
To see the current time anywhere in the world, use the World Clock widget in Today view in Notification Center or in Dashboard. For more information, see Use Notification Center or Get quick info with Dashboard.
To set the date and time format, choose Apple menu > System Preferences, then click Language & Region.