Why your computer's time matters for security
Your computer's clock does more than show you what time it is. It controls when passwords expire, when security certificates are valid, when backups run, and when your device locks itself. If your clock is wrong by more than a few minutes, your security software may stop working properly, websites may refuse to connect, and you may not be able to log in at all.
Most computers sync their time automatically with internet time servers, so you rarely have to think about it. But if your clock has drifted or you moved to a different time zone, you need to know how to fix it yourself. The steps differ between Windows and Mac, and the settings are buried in places most people never look.
Key Takeaways
- Windows computers sync time automatically through Settings > Time & Language > Date & Time, where you can also turn off automatic sync if you need manual control.
- Mac computers sync time through System Settings > General > Date & Time, and you should leave "Set date and time automatically" turned on unless you have a specific reason to change it.
- If your clock is more than 15 minutes off, some websites and security features will stop working until you fix it.
- Changing your time zone is separate from changing the actual time — both are in the same settings menu but do different things.
How to change the time on Windows 11
Open Settings by pressing the Windows key and typing "Settings", then click the Settings app. Once it opens, click Time & Language in the left sidebar, then click Date & Time.
You will see a toggle that says Set time automatically. If it is already on (the toggle is blue), your computer is syncing with an internet time server and your clock should be correct. If the time still looks wrong, click the toggle to turn it off, wait a few seconds, then turn it back on — this forces a fresh sync.
If you need to set the time manually, make sure the Set time automatically toggle is off. Then scroll down and click Change under "Set the date and time manually". A small window will pop up where you can type in the correct date and time. Click the date field first, then the time field, enter what you need, and click the checkmark to save.
Below that same section, you will see Time zone. Click the dropdown and select your time zone from the list. This is separate from the actual time — if you move to a new city, you change your time zone here, not by manually adjusting the clock.
How to change the time on Mac
Click the Apple menu in the top left corner and select System Settings. Click General in the sidebar, then scroll down and click Date & Time.
You will see a checkbox that says Set date and time automatically. Leave this on unless you have a specific reason to turn it off — most people should never need to change it. If your time looks wrong and this box is already checked, click it to uncheck it, wait a few seconds, then check it again to force a sync.
If you must set the time manually, uncheck the Set date and time automatically box. Then click the date and time fields below it and type in the correct information. When you are done, check the box again to turn automatic syncing back on.
Your time zone is in the same window. Click the Time zone dropdown and select the zone where you are located. If you travel frequently, you can turn on Set timezone automatically using current location, though this requires your Mac to have location services on.
What to do if your clock keeps drifting
If you keep having to fix your time, your computer's internal clock battery may be failing. This is a hardware problem, not a settings problem, and it usually only happens on older computers that have been off for long periods.
The easiest fix is to make sure automatic time sync is turned on and leave it that way. Your computer will correct itself every time it connects to the internet. If automatic sync is on and your time still drifts within hours, your computer may need service — contact the manufacturer or a local repair shop.
If you are using a work computer, your IT department may have locked the time settings so you cannot change them manually. If that is the case, contact them before trying to adjust anything.
Why websites reject you when your time is wrong
Security certificates on websites have a start date and an end date. If your computer's clock says the date is before the certificate started or after it expired, your browser will refuse to connect and show an error message. This is a safety feature — it prevents you from connecting to a fake website that is pretending to be real.
The same thing happens with password managers and two-factor authentication apps. If your clock is off by more than a few minutes, the time-based codes they generate will not match what the server expects, and you will not be able to log in. Fixing your clock usually fixes the problem when ready.
Frequently Asked Questions
Will changing my time zone affect my files or backups?
No. Changing your time zone only changes how your computer displays the time. Your files keep their original timestamps, and backups continue on their normal schedule. The only thing that changes is what the clock on your screen shows.
What if I cannot find Date & Time in Settings?
On Windows, make sure you clicked Time & Language first, then Date & Time — they are two separate steps. On Mac, make sure you are in System Settings, not System Preferences (older Macs use Preferences instead). If you still cannot find it, search for "date and time" in the Settings search box at the top.
Can I set my computer to a different time zone than where I actually am?
Yes, but do not do it unless you have a specific reason. Your computer uses the time zone to schedule backups, run updates, and time-stamp files. If your time zone does not match your actual location, these things may happen at inconvenient times or cause confusion when you share files with others.
Does automatic time sync use a lot of data?
No. Syncing with an internet time server uses only a tiny amount of data — less than a kilobyte per sync. It happens in the background and you will not notice it. Leaving automatic sync on is always the better choice than managing the time manually.