The fastest way to change your computer's time

On Windows, click the time in the bottom right corner of your screen, then click "Change date and time settings." On Mac, go to System Settings (or System Preferences on older versions), select "General," then "Date & Time," and make your changes there. Both operating systems let you change the time manually, but both also offer an automatic option that syncs your clock to the internet—which is usually the better choice because it keeps your time accurate without you having to think about it.

If you just need a quick fix and don't want to dig into settings, the clock in your system tray (Windows) or menu bar (Mac) is your starting point. A few clicks gets you where you need to be.

Key Takeaways

  • Windows users click the time in the taskbar and select "Change date and time settings" to adjust manually or turn on automatic syncing.
  • Mac users open System Settings, go to "General," then "Date & Time," and can toggle automatic time updates on or off.
  • Turning on automatic time synchronization means your computer stays accurate without manual adjustments, and is the recommended approach.
  • If your time keeps resetting or won't change, your computer's internal battery may be failing and needs professional attention.

Changing the time manually on Windows

Right-click the time display in the bottom right corner of your taskbar. Select "Adjust date/time" from the menu that appears. This opens the Date & Time settings panel. Under "Time," you'll see the current time displayed. Click the time itself and a text field appears where you can type in the correct hour, minute, and second. Windows uses 24-hour format by default, so 2 p.m. shows as 14:00.

Once you've entered the correct time, click outside the field or press Enter to confirm. The change takes effect when ready. If you need to change the date as well, the date field sits right above the time field and works the same way—click it, type the new date, and confirm.

Changing the time manually on Mac

Open System Settings (or System Preferences on Mac OS Monterey and earlier). Click "General" in the sidebar, then select "Date & Time." You'll see the current date and time displayed. Click the lock icon in the bottom right corner of the window and enter your Mac password to unlock the settings—this prevents accidental changes.

Once unlocked, click the date or time field and a calendar or clock picker appears. For the time, you can click the hour, minute, or second field and type the correct number, or use the up and down arrows to adjust. For the date, click the date field and a calendar opens where you can select the correct day. Confirm your changes and the new time takes effect right away.

Why automatic time synchronization is usually the better choice

Both Windows and Mac offer an automatic option that syncs your computer's clock to internet time servers. On Windows, this is called "Set time automatically" and appears as a toggle in the Date & Time settings. On Mac, it's "Set date and time automatically" in the same Date & Time panel. When this is turned on, your computer checks the correct time periodically and adjusts itself without any action from you.

Automatic synchronization is worth using because it removes the need to remember to update your clock when daylight saving time changes, and it keeps your time accurate to within a second. The only reason to turn it off is if you're troubleshooting a specific problem or if your internet connection is unreliable. For most people, leaving it on is the simplest approach.

What to do if your time keeps changing back

If you change the time manually and it reverts to the wrong time after a restart, your computer's internal clock battery is likely failing. This battery (called a CMOS battery on Windows machines and a coin-cell battery on Macs) keeps the system clock running even when the computer is powered off. When it dies, the computer forgets the time and reverts to a default when you turn it back on.

If this is happening, you have two options: turn on automatic time synchronization so your computer corrects itself every time it connects to the internet, or take your computer to a repair technician to have the battery replaced. The automatic option is the cheaper and faster fix if you have a reliable internet connection. Battery replacement is a more permanent solution but requires opening the computer, which most people should leave to a professional.

Changing your time zone

If you've moved to a different time zone or travel frequently, you may need to change your time zone setting rather than the time itself. On Windows, open Date & Time settings and scroll down to "Time zone." Click the dropdown and select your new time zone from the list. Windows will automatically adjust your clock to the correct time for that zone.

On Mac, open Date & Time settings, unlock the panel with your password, and click the "Time zone" dropdown. Type the name of your city or region and Mac will show matching time zones. Select the correct one and your clock updates automatically. If you travel often, you can turn off automatic time zone detection and manually select your zone each time you arrive somewhere new, or leave it on and let your Mac figure it out based on your location.

When to call a professional

If your computer's time won't change no matter what you do, or if it changes and then reverts when ready, the problem is usually a failing internal battery rather than a software issue. You can try restarting your computer first—sometimes a restart clears a stuck setting. If that doesn't work, take your computer to a repair technician. They can test the battery and replace it if needed, which usually takes an hour or less.

You should also see a professional if your computer is very old and the battery has never been replaced. Even if the time is currently correct, an aging battery will fail soon, and replacing it now prevents the problem from appearing at an inconvenient moment.

Frequently Asked Questions

Why does my computer show the wrong time even though I set it correctly?

If the time reverts after you restart, your internal clock battery is dying and can't hold the time when power is off. Turn on automatic time synchronization so your computer corrects itself when it boots up, or have a technician replace the battery. If the time changes while your computer is running, check that automatic synchronization isn't overriding your manual change.

Can I change the time format from 24-hour to 12-hour?

Yes. On Windows, go to Date & Time settings, scroll to "Related settings," and click "Additional date, time & regional settings." Select "Change date and time formats" and choose your preferred format from the dropdown. On Mac, open Date & Time settings and look for a "Time format" option in the panel. The exact location varies by Mac OS version.

What happens if I set my computer's time to the wrong date?

Your computer will function normally, but some programs may behave oddly. Websites might refuse to load if they think your clock is too far off, email timestamps will be wrong, and file backups may not work correctly. Set it back to the correct date as soon as you notice. If you're testing something and need to change the date temporarily, do it on a computer you're not using for important work.

Does changing the time affect my files or programs?

Changing the time itself won't damage files or programs. However, if you set the date far in the past or future, some programs that check the system date may refuse to run, and scheduled tasks may not trigger correctly. Once you set the date back to normal, everything returns to working order.