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I just installed Debian (Wheezy) on a Windows XP machine and am dual booting. But the clock is different! It's one hour late on XP versus Debian.
I'm in Paris (GMT +1) and we're in winter (daylight saving time).
I believe I set the time correctly in Debian but I'm not sure. Is it possible that Windows detects the daylight savings time and not Debian?
How to set it correctly so that I don't need to change the clock every time I change OSses?
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That is correct: PC BIOSes have no concept of UTC vs local time and just store a timestamp, uninterpreted. Both OSes might be configured to interpret BIOS time as either UTC or localtime -- the Windows configuration is explained here. The only "trick" is that both dual-bootes OSes just should agree on the same interpretation. The difference is that Debian's installer defaults to UTC while Windows installer defaults to local time.
– kostix – 2014-03-06T17:52:01.593Another point of interest is that when you're setting up a virtual machine in the VirtualBox GUI, its setting for the BIOS time interpretation will depend on the selected OS flavor: for Linux it will be UTC and for Windows it will be localtime. – kostix – 2014-03-06T17:52:50.923