Clock problems caused by dual booting with Windows

Clock problems caused by dual booting with Windows

Linux stores the raw UTC time in the BIOS clock and then interprets it according to locality, time of year and user preference. Microsoft Windows stores the local time in the BIOS clock. Windows keeps track of whether it has changed the clock for British Summer Time (you may know that as Daylight Saving Time or some other silly name for the ridiculous practice of changing the clocks twice a year). When working on a dual boot system, Linux and Windows fight over the clock.

Since I live in GMT for half the year and BST for the other half, for the BST part of the year the clock is always wrong when I boot into Windows. The solution appears to be:

• in regedit in Windows, create in [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation] a value "RealTimeIsUniversal" of type dword with a value of 1.
• prevent Windows from updating the BIOS clock with:

sc config w32time start= disabled

• Do not let Windows set the clock using the internet time.

What all this does outside GMT I do not know.