Why Your Computer's Clock Drifts and How to Reset It

Your computer's clock can fall behind or jump ahead for a few common reasons: the internal battery that keeps time running when the machine is off has died, your system hasn't synced with an internet time server in weeks, or you manually changed the time and forgot to change it back. The fix depends on which problem you have, but most of the time you can reset it in under a minute through your operating system's settings.

If your clock is wrong by hours or days, the fastest fix is to let your computer sync automatically with an internet time server. If it keeps drifting even after you sync, your internal battery may be failing and you'll need to replace it—but that's a hardware repair, not a settings fix. This guide covers the software side: how to set the time manually and how to turn on automatic syncing so it stays correct.

Key Takeaways

  • On Windows, open Settings, go to Time & Language, and toggle on "Set time automatically" to sync with an internet server in seconds.
  • On Mac, open System Settings, click General, then Date & Time, and check "Set date and time automatically."
  • If automatic sync is already on but your clock is still wrong, restart your computer to force a fresh sync with the time server.
  • If your clock loses time within hours of restarting, your computer's internal battery is likely dead and needs replacement by a technician.
  • You can also set the time manually in the same settings menu if you need to adjust it to a different time zone or correct a small drift.

Fix the Time on Windows 10 or 11

Open the Start menu and type "time" into the search box. Click "Change the time and date" when it appears. This opens the Date & Time settings panel.

Look for the toggle labeled "Set time automatically" near the top of the window. If it is already on (the toggle will be blue), your computer should sync with an internet time server every time it connects to the network. If the toggle is off, click it once to turn it on. Windows will contact a time server and update your clock within a few seconds.

If you need to set the time manually instead—for example, if you're in a time zone that Windows didn't detect correctly—click "Change" under "Set the time manually." A small window will open where you can type in the correct date and time. Click "Change" again to save it.

Fix the Time on Mac

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

Look for the checkbox next to "Set date and time automatically." If it is unchecked, click it to turn on automatic syncing. Your Mac will contact an internet time server and update the clock right away. If the checkbox is already checked but your time is still wrong, try restarting your Mac—sometimes the sync fails silently and a restart forces it to try again.

To set the time manually, uncheck "Set date and time automatically" first. Then click the date and time fields and type in the correct values. When you're done, you can check the box again to turn automatic syncing back on.

Restart Your Computer to Force a Time Sync

If your clock is wrong even though automatic syncing is turned on, restart your computer. During startup, your system will contact the time server before it finishes loading, which often fixes a clock that drifted while the machine was asleep.

Shut down your computer completely—don't just put it to sleep. Wait 10 seconds, then turn it back on. Once it finishes starting up, check the time in the bottom-right corner (Windows) or top-right corner (Mac). If it's now correct, the sync worked.

Check Your Internet Connection

Automatic time syncing requires an active internet connection. If your computer is offline, it can't reach the time server and the clock won't update. Check that you're connected to Wi-Fi or Ethernet before you turn on automatic syncing.

If you're connected but the time still won't sync, try disconnecting and reconnecting to your network. On Windows, click the network icon in the bottom-right corner, find your Wi-Fi network, and click "Disconnect," then "Connect." On Mac, click the Wi-Fi icon in the top-right corner, turn Wi-Fi off, wait 5 seconds, then turn it back on. After reconnecting, wait 30 seconds for the sync to complete.

When the Clock Keeps Losing Time

If your computer's clock falls behind by several minutes or hours within a day or two of restarting, the internal battery that powers the clock when the machine is off is likely dead or dying. This battery is separate from your main battery (on laptops) or power supply (on desktops) and keeps the system clock running even when the computer is unplugged.

When this battery fails, the clock resets to a default date and time every time you shut down. You can keep syncing the time through settings, but it will drift again as soon as you turn the computer off. The only permanent fix is to have a technician replace the battery, which usually costs between $50 and $150 depending on your machine. Until then, you can keep the time correct by syncing it every time you start up.

Adjust Your Time Zone

If your clock shows the right time but in the wrong time zone, you can change the time zone setting without changing the actual time. On Windows, open Time & Language settings, scroll down to "Time zone," and click the dropdown to select your zone. Windows will automatically adjust the displayed time to match.

On Mac, open Date & Time settings and look for the "Time zone" section. Click the dropdown and search for your city or time zone. Mac will update the displayed time right away. Make sure "Set date and time automatically" is still checked, because some Macs will re-sync the time after you change the zone.

Frequently Asked Questions

Why does my computer's time change on its own?

If automatic syncing is on, your computer updates the time whenever it connects to the internet. If the time jumps by a large amount (more than a few seconds), it usually means your clock was significantly wrong and the sync corrected it. If the time changes by an hour, you may have crossed a time zone or daylight saving time just changed.

Can I set the time to something other than the real time?

Yes, you can set it manually in Date & Time settings. However, if automatic syncing is on, your computer will override your manual change the next time it connects to the internet. Turn off automatic syncing first if you want to keep a custom time.

What if my computer says the time is correct but my phone shows a different time?

Your phone and computer sync with different time servers and may update at different times. Wait a few minutes and check again—both devices should eventually show the same time. If they stay different, check that both are set to the same time zone and that automatic syncing is on for both.

Does changing the time affect my files or programs?

Changing the system time can confuse some programs that rely on accurate timestamps, like backup software or security tools. It's best to let automatic syncing keep your time correct rather than setting it manually. If you must set it manually, do so briefly and then sync again as soon as you can.

How often should I sync my computer's time?

With automatic syncing on, your computer syncs every time it connects to the internet, usually several times a day. This is frequent enough that your clock should never drift by more than a few seconds. You don't need to do anything manually.