A few questions to make your problem more clear:
1. If the date/time is correctly set in WIndows before sleep and you set it to sleep and wake it up again, what's the new date?
2. Is the date correct after shutdown/startup and hibernate/wake? Or is is wrong then also?
3. Probably you tell us about the time shown in Windows. What's the time in the BIOS?
I have a one year old Asus computer running on Windows 10 that keeps changing the date every time it goes to sleep mode. The problem is as old as the computer. Could someone tell me what is causing this problem? Thank you

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