Ubuntu keeps resetting time to -3 hours

It sounds like you are in a timezone 3 hours separate from UTC, and Windows and Linux are disagreeing about what time should be stored in the BIOS.

Linux stores time as UTC in the BIOS clock.

Windows stores time as local time.

So whenever you boot Windows, it resets the BIOS clock to local time, Linux loads it and assumes it's UTC.

I was under the impression that the Ubuntu installer would detect Windows and set Linux to compromise by using local time in the BIOS... but this may not be true, or may not have happened correctly.

There are two solutions :

• Set Windows to use UTC in the BIOS clock

This apparently has some caveats for "professional" usage but might be satisfactory from a user POV.

https://superuser.com/questions/185773/does-windows-7-support-utc-as-bios-time

• Set Linux to use local time in the BIOS clock

Set the UTC setting in /etc/default/rcS to "no" (on Ubuntu)