Windows 7 system reverts back to 1/1/1900

Thank you for the quick response.
I can set the time from inside Windows and when I reboot the system the EFI (no BIOS) shows the correct date.
The behaviour is also observed while working (not only after system boot up) so I don't think that changing the battery will help.

Unbelievable, I may have just found the cause of the issue!
Gigabyte's AppCenter has one setting (on by default) to Auto Sync time.
For an unknown reason, it decides from time to time to go back a century or so.
Below is the evidence from the Windows Security Log (changing the date to 31/12/1899 !!!):

Log Name: Security
Source: Microsoft-Windows-Security-Auditing
Date: 1/1/1900 01:00:00
Event ID: 4616
Task Category: Security State Change
Level: Information
Keywords: Audit Success
User: N/A
Computer: XXX
Description:
The system time was changed.

Subject:
Security ID: SYSTEM
Account Name: XXX$
Account Domain: WORKGROUP
Logon ID: 0x3e7

Process Information:
Process ID: 0x5ac
Name: C:\Program Files (x86)\Gigabyte\AppCenter\AdjustService.exe

Previous Time: ‎2014‎-‎06‎-‎04T16:25:56.456160600Z
New Time: ‎1899‎-‎12‎-‎31T23:00:00.000000000Z

This event is generated when the system time is changed. It is normal for the Windows Time Service, which runs with System privilege, to change the system time on a regular basis. Other system time changes may be indicative of attempts to tamper with the computer.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
<System>
<Provider Name="Microsoft-Windows-Security-Auditing" Guid="{54849625-5478-4994-A5BA-3E3B0328C30D}" />
<EventID>4616</EventID>
<Version>1</Version>
<Level>0</Level>
<Task>12288</Task>
<Opcode>0</Opcode>
<Keywords>0x8020000000000000</Keywords>
<TimeCreated SystemTime="1899-12-31T23:00:00.001000000Z" />
<EventRecordID>6208</EventRecordID>
<Correlation />
<Execution ProcessID="4" ThreadID="88" />
<Channel>Security</Channel>
<Computer>XXX</Computer>
<Security />
</System>
<EventData>
<Data Name="SubjectUserSid">S-1-5-18</Data>
<Data Name="SubjectUserName">XXX$</Data>
<Data Name="SubjectDomainName">WORKGROUP</Data>
<Data Name="SubjectLogonId">0x3e7</Data>
<Data Name="PreviousTime">2014-06-04T16:25:56.456160600Z</Data>
<Data Name="NewTime">1899-12-31T23:00:00.000000000Z</Data>
<Data Name="ProcessId">0x5ac</Data>
<Data Name="ProcessName">C:\Program Files (x86)\Gigabyte\AppCenter\AdjustService.exe</Data>
</EventData>
</Event>

Dear StylianosIordan,
apologies for the delayed response, astanapane is right.
Please let me know if you have any issues and I will post screen shots.
Kind regards.

Hello Nikos1979,
please read messages below.
The solution is there!
Kind regards,
Kyriakos