Windows and Mac both let you change the system clock in Settings, though the exact steps differ between them

Your PC clock drifts out of sync for straightforward reasons: the battery that powers the clock chip when your computer is off has weakened, your system clock was never set correctly, or you moved to a different time zone. The fix takes less than a minute on either Windows or Mac, and you can do it yourself without opening the computer or calling anyone.

Most of the time, your PC syncs automatically with an internet time server, so the clock corrects itself without you noticing. But if automatic sync is turned off, or if the battery on your motherboard is failing, you will need to set it manually. The steps below cover both Windows 11 and macOS, and older versions follow nearly the same path.

Key Takeaways

  • Windows 11 clock settings are found in Settings > Time & Language > Date & Time, where you can toggle automatic sync on or off and set the time manually.
  • macOS clock settings are in System Settings > General > Date & Time, and you can choose to set the time automatically or enter it by hand.
  • If your clock keeps drifting even after you set it, the coin-cell battery on your motherboard may be failing and will need replacement by a technician.
  • Automatic time sync uses internet time servers and keeps your clock accurate without any action from you, so turning it on is usually the best solution.

How to change the clock on Windows 11

Open Settings by pressing the Windows key and typing "Settings," then click the Settings app. Go to Time & Language in the left sidebar, then click Date & Time. You will see a toggle for Set time automatically — if it is already on, your clock should sync with an internet time server and correct itself. If it is off, turn it on.

If you need to set the time by hand, turn off the Set time automatically toggle first. A new option called Set the date and time manually will appear below it. Click that option, and you will see fields for the date and time. Enter the correct values and click Done. Your clock will now show the time you entered.

While you are in Date & Time settings, check that your time zone is correct. Scroll down to find Time zone and make sure it matches where you are. If you moved and the zone did not update, click the dropdown and select the right one. Windows will then adjust the displayed time to match.

How to change the clock on macOS

Click the Apple menu in the top-left corner and select System Settings. In the sidebar, click General, then select Date & Time. You will see a checkbox for Set date and time automatically — if it is checked, your Mac is syncing with an internet time server and you do not need to do anything else.

If the automatic option is unchecked, click the checkbox to turn it on. If you must set the time manually instead, leave the checkbox unchecked and click the date and time fields to edit them. Enter the correct date and time, then close the window. Your Mac will use the values you entered.

Check your time zone as well. In the same Date & Time window, look for the Time zone setting and click it to see a list of zones. Select the one that matches your location. macOS will adjust the displayed time once you choose.

Why your clock keeps drifting even after you set it

If you set the time correctly but it drifts again within hours or days, the problem is usually a failing CMOS battery — a small coin-cell battery on your motherboard that keeps the clock running when the computer is powered off. When this battery weakens, the clock loses time and resets when you shut down.

You can confirm this is the issue by setting the time, shutting down the computer, waiting an hour, and turning it back on. If the clock has reverted to an earlier time, the CMOS battery is failing. Replacing it requires opening the computer case and locating the battery on the motherboard — a task best left to a technician or someone comfortable with computer hardware. The battery itself costs a few dollars, but the labor may run higher depending on your computer's design.

Until you replace the battery, you can work around the problem by turning on automatic time sync. Your clock will still be wrong when you first start the computer, but it will correct itself within a few seconds once you connect to the internet.

Turning on automatic time sync if it keeps turning itself off

Some computers have automatic time sync turned off by default, or it gets disabled by security software or system updates. If you turn it on but it switches back off on its own, check whether a third-party security program is managing your time settings. Antivirus software, firewalls, and system optimization tools sometimes lock down the clock to prevent malware from tampering with it.

Open your security software and look for settings related to system protection, firewall, or advanced options. If you find a setting that controls the system clock, check whether it is set to manual mode. Switch it to automatic if the option is available. If you cannot find the setting or the software does not offer one, you may need to temporarily disable the software to turn on automatic sync, or contact the software maker for help.

If no security software is running and automatic sync still will not stay on, the issue may be a corrupted Windows or macOS system file. In that case, a technician can help diagnose and repair the problem, though it is rare.

What to do if the time zone is wrong but you cannot change it

On Windows, if the time zone dropdown is grayed out or will not let you select a different zone, your computer may be set to sync time zone automatically based on your location. Look for a toggle called Set time zone automatically and turn it off. You should then be able to click the time zone dropdown and choose manually.

On macOS, the time zone field may be locked if you have parental controls or security restrictions enabled. Check System Settings > General > Date & Time to see whether a lock icon appears next to the time zone field. If it does, click the lock, enter your admin password, and you will be able to change the zone.

Frequently Asked Questions

Will changing my PC clock affect my files or programs?

Changing the system clock can affect file timestamps and some programs that rely on accurate time, such as email clients or security software. In general, moving the clock forward or backward by a few minutes causes no problems. Moving it by hours or days may confuse backup software or cause scheduled tasks to behave unexpectedly. Set it to the correct time and leave it there.

What is the difference between UTC and my local time zone?

UTC (Coordinated Universal Time) is the global standard time used by computers and networks. Your local time zone is UTC plus or minus a number of hours depending on where you are. Your PC stores time internally as UTC but displays it in your local zone. You should always set your time zone to match your location, not change it to UTC.

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

Yes. On Windows, go to Settings > Time & Language > Date & Time, scroll down to Related settings, and click Additional date, time & regional settings. Click Change date and time formats and choose your preferred format. On macOS, open System Settings > General > Date & Time and look for a clock format option in the same window.

Why does my clock show the wrong time even though automatic sync is on?

If automatic sync is on but the time is still wrong, your computer may not have internet access, or the time server may be unreachable. Check that you are connected to the internet. If you are connected and the time still does not update after a few minutes, restart your computer. If the problem persists, the CMOS battery may be failing and will need replacement.