If the BIOS clock resets after shutdown or when power is removed, start by checking the coin-cell battery or other RTC backup power source, then verify whether the time survives a full power-loss test. This can affect logins, certificate checks, file timestamps, and update validation. Use the steps below to separate a clock-retention problem from a Windows time-setting issue before you consider firmware changes.
What BIOS date and time resetting usually means
BIOS date and time are stored in firmware, not Windows. BIOS stands for Basic Input/Output System, and BIOS firmware is used during the booting process. UEFI is the successor to legacy PC BIOS, and many newer systems store firmware contents on flash memory, so a reset usually points to retained settings or backup power rather than a Windows clock issue. (en.wikipedia.org)
Likely causes ranked by symptom pattern
| Symptom pattern | Likely cause | Next step |
|---|---|---|
| Resets only when unplugged | Backup battery or RTC backup power is not holding settings | Replace the battery, then recheck the time after a full power loss |
| Resets after shutdown | Power-retention problem | Verify the PSU switch, AC cable, and battery condition |
| Drift while powered on | RTC drift or firmware timing issue | Confirm whether the clock changes inside BIOS/UEFI itself |
| Settings do not save | Firmware settings problem | Load defaults if the manual supports it, then check firmware version |
Small examples that help separate the fault
Say your desktop keeps the correct time all day, then loses it after you switch off the PSU at the back. That points away from Windows and toward the backup-power path for firmware settings. Suppose the time is wrong even before Windows starts, but only by a few minutes each week; that looks more like drift than a full reset.
📊 BIOS version can be checked with msinfo32. Source: How to Check Your BIOS Version and Update it.
Why does BIOS date and time keep resetting after shutdown?
A reset after shutdown usually means the firmware clock did not keep its saved state while the machine was off. The fastest first check is the backup battery, because it supports the clock and settings when the PC is off; if the clock returns only after a full power loss, move next to the PSU switch, AC cord, and board power retention.
Check the CMOS battery first
- Shut the PC down using the normal Windows power menu.
- Unplug AC power from the PC.
- Switch the PSU off if the system has one.
- Wait briefly, then reconnect power and start the PC.
- Enter BIOS/UEFI and check whether the date and time changed.
If the reset appears after that full power-off test, replace the CMOS battery or battery pack. That is the primary hardware fix when the clock drops after power loss.
How to check the CMOS battery and replace it
The CMOS battery is usually a coin-cell battery, but some compact systems use a wired onboard battery pack. Use the same form factor when you replace it, and reinstall it in the same orientation. If the battery is buried under a GPU, shroud, or bracket, access may be the limiting factor rather than the battery itself.
Replacement steps
- Power off the PC, unplug AC power, and switch the PSU off if the system has one.
- Open the case or service panel and find the battery or battery pack on the motherboard.
- Remove the old battery carefully.
- Install the replacement with the same form factor and the same orientation.
- Restore power, enter BIOS/UEFI, set the correct date and time, then save and exit.
- After that, let the PC boot normally and then shut it down again to confirm the time survives a reboot and a shutdown cycle.
A common first-timer mistake is reversing the coin-cell orientation or fitting the wrong size battery. That can leave the firmware settings unpowered and make the clock reset again on the next unplug.
How to fix BIOS date and time resetting
Start by separating a BIOS/UEFI clock problem from a Windows time-sync problem. If the time is wrong inside firmware before Windows loads, Windows Update or automatic time sync is not the root cause. If the time is correct in BIOS but wrong in Windows, then the issue is in Windows time settings, not the firmware clock.
Enter BIOS/UEFI with a startup key or Windows recovery
- Restart the PC.
- Press the manufacturer BIOS key during startup; common BIOS keys include Del, F2, F10, Esc, and F12.
- If you miss the key, open Windows 10 or 11 Advanced Startup from Settings or the sign-in screen power menu.
- Choose Troubleshoot > Advanced Options > UEFI Firmware Settings.
- On the Advanced Startup path, use Restart Now in Recovery when prompted.
Many newer PCs use UEFI instead of legacy BIOS. Microsoft Surface tablets use the Volume Up button for BIOS access. Tom's Hardware notes that most modern motherboards use the DEL key, and BIOS access may also be needed to enable virtualization.
When to load defaults
- Enter BIOS/UEFI.
- Look for a menu item such as Load Optimized Defaults or Restore Defaults.
- Use it only if the motherboard manual supports that step for your model.
- Save changes and exit.
- Recheck the time after a reboot and a shutdown cycle.
Suppose the clock is stable after loading defaults but begins resetting again only after a power loss. That pattern still points back to the backup-power path, not Windows.
Decision tree for clock reset symptoms
Use the table below to move from symptom to likely cause without guessing. The point is to separate unplug behavior, shutdown behavior, drift, and save failures before you consider firmware flashing.
| Symptom pattern | Likely cause | Best next move |
|---|---|---|
| Resets only when unplugged | Backup battery failure or battery pack failure | Replace the battery first |
| Resets after full shutdown or PSU switch-off | RTC power loss or weak battery-backed retention | Check battery, AC power path, and PSU switch behavior |
| Drift while the PC is powered on | RTC drift or firmware timing fault | Confirm the clock in BIOS, then compare against firmware version notes |
| Settings do not save after exit | Firmware settings problem | Try defaults if supported, then inspect firmware update notes |
| Time resets after changing a setting | Weak battery or unstable firmware storage | Replace the CMOS battery before any BIOS flash |
Do you need a BIOS update?
Only move to a BIOS update after the battery and power-loss checks rule out simple retention failure. Before any firmware change, record the current BIOS version in System Information so you can compare it later. A BIOS update may fix RTC, power-loss, stability, or settings issues, but a failed flash can brick a computer if it is interrupted.
Check the BIOS version and read the support notes
- Press Windows key + R.
- Type msinfo32 and press Enter.
- Record the BIOS Version/Date field before any change.
- Visit the motherboard or PC maker support page.
- Read the release notes for RTC, power-loss, stability, or settings fixes.
- Update only if the notes match the symptom pattern.
- Do not interrupt the flash, and do not update from a battery that is low or from unstable wall power.
How-To Geek warns that a failed BIOS update can brick a computer. That risk is why the update step belongs near the end of the fault tree, not at the start.
Can Windows update cause BIOS time to reset?
Windows updates do not usually clear the firmware clock, since BIOS/UEFI time is stored outside Windows. If the BIOS time itself resets or drifts before Windows loads, the problem is elsewhere. If Windows time is wrong but BIOS time is correct, focus on Windows time settings instead of the motherboard firmware.
Check the right layer
- Restart into BIOS/UEFI and note the displayed time.
- Boot into Windows and check the clock again.
- If BIOS is correct and Windows is wrong, open Settings > Time & language > Date & time.
- If BIOS is wrong too, return to the battery and firmware checks above.
How do I enter BIOS on Windows 10 or 11 to change the time?
Use the startup key first, since it is often the quickest route. If you miss it, Windows 10 and Windows 11 can open UEFI Firmware Settings from Advanced Startup. The exact recovery path differs by version, so use the one that matches your system rather than a single generic menu path.
Windows 11 path
- Open Settings.
- Go to System > Recovery.
- Under Advanced startup, choose Restart now.
- Select Troubleshoot > Advanced options > UEFI Firmware Settings.
Windows 10 path
- Open Settings.
- Go to Update & Security > Recovery.
- Under Advanced startup, choose Restart now.
- Select Troubleshoot > Advanced options > UEFI Firmware Settings.
Still not working?
If the clock still resets after a new battery and a verified firmware check, move to board-specific battery packs or a motherboard fault. At that point, the problem may be beyond a simple replacement part. A vendor support channel or repair shop is the next step if the board uses an unusual battery assembly or if the BIOS cannot hold settings at all.
Escalation ladder
- Verify the battery type again and confirm it is seated correctly.
- Check whether the motherboard uses a wired battery pack instead of a coin cell.
- Confirm the PSU switch, AC cable, and wall power are stable.
- Revisit the support page for a firmware release tied to RTC or settings retention.
- Seek board-level service if settings still vanish after the battery and firmware checks.
A practical check is to shut the PC down using the normal power menu after any battery replacement or BIOS change, then confirm the clock still survives a power-off cycle before closing the case.
Frequently asked questions
Why does BIOS date and time keep resetting?
It usually means the firmware clock is not keeping its saved state while the PC is off. Check the CMOS battery first, then confirm whether the problem appears only after unplugging or also after a normal shutdown. If BIOS itself shows the wrong time, Windows time sync is not the cause.
Why does BIOS date and time keep resetting after shutdown?
A reset after shutdown points to lost settings while the system is off. Shut the PC down using the normal power menu, disconnect AC power, wait briefly, and reconnect it. If the clock changes after that test, replace the CMOS battery or battery pack, then set the time again in BIOS/UEFI.
Why is my BIOS date and time always wrong?
If it is wrong every time you enter firmware, the RTC is not holding the clock or the settings are not being saved. Check the battery first, then open System Information with msinfo32 and record BIOS Version/Date. If the board has a relevant update note, apply it after the battery check.
Is a dead CMOS battery causing the BIOS clock to reset?
A dead CMOS battery is a common reason when the clock resets after power loss. Replace the CMOS battery with the same form factor and reinstall it in the same orientation. Afterward, set the time in BIOS/UEFI and verify that it survives a full shutdown and unplug cycle.
How do I fix BIOS date and time resetting?
Start with a full power-off test, then replace the CMOS battery if the clock fails after unplugging or PSU-off. If the battery is good, check whether settings save inside BIOS/UEFI and compare the installed firmware version with the motherboard support page. Update only if the release notes mention RTC, power-loss, or settings fixes.
Can Windows update cause BIOS time to reset?
Windows Update does not normally reset firmware time, because BIOS/UEFI keeps its own clock outside Windows. If Windows time is wrong but BIOS time is correct, open Settings > Time & language > Date & time. If BIOS time itself is wrong, return to battery and firmware checks instead.