On a dual boot Windows/Linux box the BIOS time must be the local time as Windows do not support having a system time different thant the hardware time. So what happened when the time change because of daylight saving ?
- Boot on linux
- Starting network interfaces call ntpdate which change the system time (+3600 or -3600 seconds)
- Shutdown linux save system time to hardware time
- Boot Windows
- Windows change the time (system and hardware as it’s the same for it) because it do not know that it was already changed. So you are now +7200 or -7200 second from the local time.