Your computer time keeps changing usually because of a dying CMOS battery, an internet time sync problem, a wrong time zone, or a dual boot conflict between Windows and Linux over how the hardware clock is stored. When the small motherboard battery weakens, the clock resets or drifts each time the computer is off. Fixing the time source or the battery stops it.
Why this happens
- A dying CMOS battery, the coin cell on the motherboard that keeps the clock running when the computer is off. When it fails, the time and date reset, often to a past date, on every startup.
- A wrong time zone, or the automatic time setting pointing to the wrong region.
- Internet time sync failing because the time service is off or cannot reach its server.
- A dual boot conflict. Windows expects the hardware clock to store local time, while Linux stores it as UTC, so booting between them keeps changing the clock.
- Daylight saving handling, which can shift the time if the settings are wrong.
- In rare cases, malware can alter system time.
Is this normal?
A tiny drift that internet sync quietly corrects is normal. Large jumps, or the clock resetting to an old date every time you start the computer, are not normal and point to one of the causes above.
Does it cause any problems?
Yes. A wrong clock can cause secure website certificate errors, failed logins, wrong file timestamps, and calendar and sync problems, so it is worth fixing.
How to fix or check it
- On Windows, right-click the clock, open date and time settings, turn on Set time automatically, and confirm the correct time zone, then choose Sync now.
- Make sure the Windows Time service is running. Open services.msc, find Windows Time, and set it to start automatically.
- On a Mac, open System Settings, General, Date and Time, turn on Set time and date automatically, and set the correct time zone.
- If the time resets to a past date on every boot, replace the CMOS coin cell battery on the motherboard.
- For a Windows and Linux dual boot, make both agree on the clock. Either set Linux to use local time, or set Windows to treat the hardware clock as UTC.
- Update the BIOS and make sure its clock is set correctly.
- If the problem persists after these steps, run a malware scan.
Frequently asked questions
The time resets to an old date every startup, what is wrong?
That is the classic sign of a dead CMOS battery. Replacing the coin cell on the motherboard usually fixes it.
Why did the time break after I installed Linux?
Windows and Linux disagree on whether the hardware clock stores local time or UTC. Set both to use the same convention to stop the shifting.
Can a wrong clock really break websites?
Yes. A clock that is off can cause certificate and security errors and failed logins, because secure connections rely on accurate time.