Exodias3219 :
I already replaced the cmos battery with a new one. Bios settings are on default. Bios Time is on 24h format. Bios date is ok.
os: windows 7 professional
There are several possibilities.
1> Windows time is set to the wrong time-zone or wrong setting for Daylight Savings Time.
2> Windows Time Sync isn't working properly.
3> Windows might be out of date.
For both, click on the clock and choose "Adjust date and time settings..."
1> Time zone will be on the Date and Time tab, Make sure it is set correctly.
2> Click the "Internet Time" tab. Is it set up to synchronize the time with time.windows.com? If it is, Click on the Change Settings button and try changing to say, time.nist.gov , save the settings and click OK. Restart to see if that fixes your problem. If it isn't selected already, try selecting time.windows.com. and then clicking OK and restarting.
3> While it might be possible this is the cause, you can eliminate it by making sure Windows has all of its updates. This might or might not have its own problems though due to Microsoft messing with the updates system since the release of Windows 10. If it is an issue, let us know.