When switching between Ubuntu OS and Windows 10 OS, there is a time difference in Windows OS. It is because Ubuntu OS sets the BIOS time to UTC, then Ubuntu calculates local time based on UTC and displays it correctly. But Windows 7 / 10 OS takes the BIOS time whatever it is and shows as Local Time.
In this case, you can solve it by following any one of the method listed below.
1. Set Windows OS to take the BIOS time as UTC
Open the Registry Editor (regedit) (Run -> regedit)
Traverse the following path, HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation
Create a dword named RealTimeIsUniversal and set the value to 1 (Right click -> new -> DWORD Value)
Restart your computer
2. Set Ubuntu / Linux OS to take BIOS time as Local time
Open terminal and execute the following command
timedatectl set-local-rtc 1
This command works on latest
This command works on latest release Ubuntu 20.04 (Focal Fossa)