Where your computer stores the time and why it matters

Your computer has a built-in clock powered by a small battery on the motherboard — the main circuit board inside. This clock keeps running even when your computer is off, which is why it can show you the correct time the moment you turn it back on. If your computer's time is wrong, it affects more than just what you see on the screen: programs that back up your files, security certificates that protect your passwords, and email timestamps all depend on an accurate system clock.

Most of the time, your computer sets itself. It connects to time servers on the internet and syncs automatically, so you never have to think about it. But if your computer is offline, the battery is dying, or the automatic sync has stopped working, you may need to set the time yourself.

Key Takeaways

  • Windows computers store time in Settings under Date & Time, and you can toggle automatic sync on or off from the same screen.
  • Mac computers use System Settings > General > Date & Time, where you can also choose to sync with an internet time server.
  • If automatic sync is on and your time is still wrong, your computer may be offline or the battery inside may be failing.
  • Changing the time manually takes less than a minute on either operating system, but automatic sync is usually the better long-term fix.

How to change the time on Windows

Open Settings by pressing the Windows key and typing "Settings", then press Enter. Click on "Time & Language" in the left menu, then click "Date & Time". You will see a toggle for "Set time automatically" — if it is already on (blue), your computer should be syncing with an internet time server and you should not need to change anything manually.

If you need to set the time yourself, turn off "Set time automatically" first. A new option called "Change" will appear below it. Click "Change", and a small window will open where you can type in the correct date and time. Enter the information and click "Change" again. Your new time takes effect when ready. If you want automatic sync to resume, toggle "Set time automatically" back on.

How to change the time on Mac

Click the Apple menu in the top-left corner and select "System Settings". Click "General" in the left sidebar, then scroll down and click "Date & Time". You will see a checkbox for "Set date and time automatically" — if it is checked, your Mac is already syncing with an internet time server.

To set the time manually, uncheck "Set date and time automatically". The date and time fields will become editable. Click on the date field or time field and type the correct information. When you are done, check the box again to turn automatic sync back on. Your Mac will sync with the time server the next time it connects to the internet.

Why automatic sync stops working

If "Set time automatically" is already on but your time is still wrong, your computer is probably not connected to the internet. Check that you are on a working Wi-Fi network or that your ethernet cable is plugged in. Restart your computer and check again — sometimes the connection drops without warning.

If you are online and the time is still wrong after restarting, the internal battery may be dying. This battery is small and lasts for years, but when it fails, your computer loses track of time the moment you shut it down. You will see the time reset to something very old (often 2000 or 2010) when you turn the computer back on. If this is happening, the battery needs to be replaced — this is a job for a repair shop, not something you can fix yourself.

When to sync with a specific time server

Most computers sync with a default time server chosen by your operating system, and this works fine for everyday use. If you work in a field where precise timing matters — video production, network administration, or scientific work — you may need to sync with a more accurate server. Both Windows and Mac allow you to specify a custom time server in their advanced date and time settings, but this is rarely necessary for personal use.

If you are in a workplace that requires a specific time server, your IT department will tell you which one to use and how to set it up. Do not change this setting on your own unless you have been asked to do so.

What to do if the time keeps changing on its own

If your time jumps forward or backward unexpectedly, even with automatic sync on, your computer may be switching between time zones. This happens most often after you travel or if your location settings are turned on. Check your time zone setting: on Windows, go to Settings > Time & Language > Date & Time and look for "Time zone". On Mac, go to System Settings > General > Date & Time and check the "Time zone" dropdown. Make sure it matches where you actually are.

If the time zone is correct and the time is still jumping around, a program on your computer may be changing it. This is rare but can happen with certain software. Restart your computer in Safe Mode (Windows) or Safe Boot (Mac) to see if the problem stops. If it does, a program you installed is the cause — uninstall recent additions one at a time until the jumping stops.

Frequently Asked Questions

Will changing the time affect my files or programs?

Changing the time can affect file timestamps and backup schedules, but it will not damage your files or break programs. However, if you set the time far in the past, some security certificates may become invalid until the time catches up again. Set the time as close to the actual time as you can.

What if my computer does not have internet access?

You will need to set the time manually. If your computer is offline permanently, you can set it once and it will keep that time as long as the internal battery is working. If the battery dies, you will need to set it again the next time you turn the computer on.

Can I set my computer to a different time zone without changing the actual time?

Yes. Change the time zone setting without touching the date and time fields themselves. Your computer will automatically adjust the displayed time to match the new zone, but the actual system time stays the same.

Why does my time reset to 2010 every time I restart?

This is a sign that the internal battery is failing. The battery keeps the clock running when your computer is off. When it dies, the computer forgets the time and resets to a default date. You will need to have the battery replaced by a repair technician.