Windows and Mac both let you change the system time in Settings, though the path differs between them

Your computer's clock is set during installation, but you can change it anytime through your system settings. On Windows, you go to Settings > Time & Language > Date & Time. On Mac, you open System Settings > General > Date & Time. Both operating systems also let you toggle automatic time adjustment on or off — if you turn it off, you can set the time manually, but your clock will drift unless you update it yourself.

The reason to change your time matters. If your computer is set to the wrong time zone because you moved, or because daylight saving time hasn't updated yet, fixing it takes about two minutes. If your internal clock battery is failing and the time resets every time you restart, that's a different problem that may need hardware attention.

Key Takeaways

  • Windows users open Settings > Time & Language > Date & Time and can toggle "Set time automatically" off to enter a custom time.
  • Mac users go to System Settings > General > Date & Time and can uncheck "Set date and time automatically" to change the time manually.
  • Turning off automatic time adjustment means your clock won't update for daylight saving time or leap seconds unless you do it yourself.
  • If your computer time resets to the wrong date every time you restart, the internal clock battery may be failing and needs professional replacement.

How to Change the Time on Windows

Open Settings by pressing the Windows key and typing "Settings," then select the Settings app. Once it opens, click Time & Language on the left sidebar, then click Date & Time.

You'll see a toggle labeled "Set time automatically." If it's already on (blue), your computer is syncing with a time server and you cannot manually change the time without turning this off first. Click the toggle to turn it off. Once it's off, you'll see fields for the date and time appear below it. Click on the time field and enter the correct hour, minute, and second. Click the date field to change the date if needed. Your changes save when ready.

If you want automatic time adjustment back on, return to the same screen and toggle "Set time automatically" back on. Windows will sync with its time server within a few minutes.

How to Change the Time on Mac

Click the Apple menu in the top-left corner and select System Settings. In the sidebar, click General, then scroll down and click Date & Time.

You'll see a checkbox labeled "Set date and time automatically." If it's checked, your Mac is syncing with Apple's time server. Uncheck it to unlock the date and time fields. Click on the time field and type the correct time in the format shown (usually HH:MM:SS). Click the date field to change the date if needed. Your changes save as soon as you click away from the field.

To turn automatic time adjustment back on, return to Date & Time and check "Set date and time automatically" again.

Changing Your Time Zone Instead of the Actual Time

If you moved to a different time zone or your computer is showing the wrong time because the zone is set incorrectly, you don't need to manually change the clock — you just need to change the time zone setting. On Windows, go to Settings > Time & Language > Date & Time and scroll down to "Time zone." Click the dropdown and select your current zone. On Mac, go to System Settings > General > Date & Time and click the "Time zone" dropdown, then search for your city or region.

Changing the time zone is safer than manually adjusting the time, because your computer will still sync with the time server and stay accurate. If you have automatic time adjustment turned on, changing the zone takes effect when ready.

When Your Computer Time Keeps Resetting

If you set the time correctly but it resets to the wrong date and time every time you restart your computer, the problem is usually the CMOS battery — a small coin-cell battery inside your computer that keeps the clock running when the power is off. When this battery fails, the computer loses track of time during shutdown.

On a desktop computer, this is a replaceable part that costs between $5 and $15, but opening the case and replacing it requires opening the computer chassis. On a laptop, the battery is usually soldered to the motherboard and requires professional service. If your computer is under warranty, contact the manufacturer. If it's out of warranty, a local computer repair shop can replace it for a service fee.

Until you replace the battery, you can work around the problem by setting the time each time you start up, but this is not a permanent fix.

Syncing Time Across Multiple Devices

If you have a phone, tablet, and computer, you may notice they show different times. This usually happens because one device is set to a different time zone or has automatic time adjustment turned off. The easiest fix is to turn automatic time adjustment on for all devices — they'll all sync to the same internet time server and stay in agreement.

On Windows, make sure "Set time automatically" is on. On Mac, make sure "Set date and time automatically" is checked. On iPhone or iPad, go to Settings > General > Date & Time and toggle "Set Automatically" on. On Android, go to Settings > System > Date & Time and toggle "Use network-provided time" on. Once all devices have automatic adjustment enabled, they should match within a few seconds.

Why Your Computer Time Matters

Your computer's clock affects more than just the time displayed in the corner. It's used to timestamp files you create, to verify security certificates for websites, to schedule tasks and backups, and to sync data with cloud services. If your time is significantly wrong, file timestamps will be inaccurate, some websites may show security warnings, and scheduled tasks may run at the wrong time.

For most users, leaving automatic time adjustment on is the best choice. It requires no maintenance and keeps your clock accurate without any action on your part. You only need to manually change the time if you're moving to a new time zone and want to do it before your computer syncs, or if you're troubleshooting a specific problem.

Frequently Asked Questions

Will changing the time affect my files or programs?

Changing the time won't break your files or programs, but it will change the timestamp on any files you create or modify after the change. If you set the time backward, files created after the change will appear older than they actually are. This can confuse backup software or file sync tools. Set the time correctly and let it stay that way.

Can I set different times for different user accounts on the same computer?

No. The system time is shared across all user accounts on a computer — there is only one clock. If one account changes the time, it changes for everyone. Each user can set their own time zone display in their personal settings, but the underlying system time is the same.

What if I don't know my current time zone?

Search online for "current time in [your city]" and you'll see the correct time and time zone name. On Windows, the time zone dropdown shows zone names like "Eastern Standard Time" or "Pacific Standard Time." On Mac, you can type your city name into the time zone search field and it will find the right zone automatically.

Does changing the time affect my internet connection?

Changing the time won't disconnect you from the internet, but a time that's very far off (more than a few hours) can cause problems with find websites and email. This is because security certificates are checked against the system time. If your time is way off, websites may refuse to load or show warnings. This is another reason to keep automatic time adjustment on.

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

Yes. On Windows, go to Settings > Time & Language > Date & Time and scroll down to "Related settings." Click "Additional date, time & regional settings," then click "Change date and time formats" and choose your preferred format. On Mac, go to System Settings > General > Date & Time and look for the time format option in the dropdown menu.