The fastest way to set the correct time

On Windows, right-click the time in the bottom-right corner of your screen and select Adjust date and time. Toggle Set time automatically to on. Windows will sync with a time server and correct itself within a few seconds. If that does not work, toggle it off, then on again.

On Mac, open System Settings, click General, then Date & Time. Check that Set date and time automatically is turned on. If the time is still wrong after waiting a minute, toggle it off and back on.

If automatic sync is already on and your time is still wrong, your computer may have lost its internet connection or your system clock battery may be failing. Check that you are connected to Wi-Fi or ethernet, wait 30 seconds, and try the toggle again.

Key Takeaways

  • Automatic time sync is the default on both Windows and Mac and works in the background without your input.
  • If automatic sync is on but your time is wrong, toggle it off and back on to force a refresh.
  • A computer that cannot hold the correct time even after restart may have a failing CMOS battery, which requires professional repair.
  • Manual time entry is rarely necessary; if automatic sync fails, the problem is usually a connection issue or a hardware fault, not a settings mistake.

Why your computer's time drifts without a network

Every computer has an internal clock powered by a small battery called a CMOS battery. This battery keeps time even when your computer is off. Over time, this battery weakens, and the clock drifts—sometimes gaining or losing several minutes per day.

When your computer connects to the internet, it syncs with a time server and corrects any drift. If you leave automatic sync on, you will not notice the drift because the correction happens in the background. If you turn automatic sync off, or if your computer is offline for days, the time will become noticeably wrong.

This is normal and not a sign of damage. The CMOS battery lasts many years in most computers. You only need to worry if your computer loses time even after you restart it and turn automatic sync back on.

Manual time entry when automatic sync does not work

If automatic sync is on but your time is still wrong after you toggle it off and back on, check your internet connection. Open a web browser and visit any website. If the page loads, your connection is working and the problem is elsewhere.

If you need to set the time manually while you troubleshoot, the process is the same place you checked automatic sync. On Windows, in Date & Time settings, click Change under the date and time display. On Mac, click the lock icon in Date & Time settings and enter your password, then adjust the time in the fields provided.

Manual entry is a temporary fix only. Once you set it by hand, it will drift again unless automatic sync is working. Do not rely on manual entry as a permanent solution.

What to do if your time resets every time you restart

If you shut down your computer, turn it back on, and the time has reverted to an earlier time (often a date from years ago), your CMOS battery is failing. This battery is a small coin-shaped cell inside your computer that keeps time when the power is off.

A failing CMOS battery cannot be replaced by most users—it requires opening the computer case and locating the battery on the motherboard. This is a job for a repair technician. Contact a local computer repair shop and describe the symptom: the time resets to an old date every time you restart. They can replace the battery in under an hour.

Until you have it repaired, you can keep your time correct by leaving automatic sync on and keeping your computer connected to the internet. The moment you disconnect or shut down, the time will drift again, but it will correct itself as soon as you reconnect.

Time zone settings and daylight saving time

If your time is correct but your time zone is wrong, or if your computer did not adjust for daylight saving time, the fix is in the same settings. On Windows, in Date & Time, scroll down to Time zone and select your zone from the dropdown. On Mac, in Date & Time, click the dropdown next to Time zone and search for your city or region.

When Set time automatically is on, your computer should adjust for daylight saving time on the correct date without your input. If it does not, toggle automatic sync off and back on to force an update.

If you travel and want to change your time zone temporarily, you can do so in the same settings. When you return home, change it back, or turn on automatic sync and let your computer detect your location from your internet connection.

Syncing time across multiple devices

If you have a phone, tablet, or other device, it syncs time the same way your computer does—through an internet connection and a time server. You do not need to sync them to each other. Each device corrects itself independently.

If one device shows a different time than another, check that both are connected to the internet and that automatic sync is on for both. Wait a minute and check again. If the times still differ, one device may have a hardware problem or may be set to a different time zone.

You do not need to manually sync devices. Turning automatic sync on and connecting to the internet is all that is required.

Frequently Asked Questions

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

Your computer may not be connected to the internet, or the time server may be unreachable. Check your Wi-Fi or ethernet connection by opening a web browser. If you can load a website, toggle automatic sync off and back on to force a refresh. If the time is still wrong after that, restart your computer and wait two minutes for it to sync.

Can I change my time zone without changing the actual time?

Yes. When you change your time zone in settings, the clock adjusts automatically to show the correct local time for that zone. The actual moment in time does not change—only what your computer displays. This is why travelers can change time zones without losing any data or causing problems.

What if my computer time is off by exactly 12 hours?

Your computer is likely set to the wrong time format—24-hour instead of 12-hour, or vice versa. Check your time format setting in Date & Time on Windows or Date & Time on Mac. You can also check whether your time zone is set correctly, as a wrong zone can cause a 12-hour offset in some cases.

Does the CMOS battery need to be replaced if my time drifts slowly?

No. Slow drift is normal and expected. The CMOS battery lasts many years. You only need to replace it if your computer loses time even after you restart it and turn automatic sync back on—meaning it cannot hold time at all, not just that it drifts a little.

Can I fix the time without restarting my computer?

Yes. Toggle automatic sync off and back on without restarting. Your computer will contact a time server and correct itself in a few seconds. A restart is only necessary if toggling sync does not work.