Solved Clock not syncronized

Running Win 11 on an iMac 8,1 dual booting with OSX 10.11. The problem is that the clock is quite accurate in date, day and minutes, but always boots 1 hour slow. I have it set to change at summer time and when made to resync with the time server, it corrects itself, but reverts on reboot. I have checked services and Win Time is set to run automatcally. I have also stopped/restarted this service On the OSX side, the clock is perfectly accurate. Any ideas?

This is a common issue when dual booting Windows with Mac OS or Linux. Windows are using a difference method of calculating UTC than Mac OS or Linux hence the one hour difference on restart, You must either set Windows to use the same method as Mac OS or the other way round.

To change it on Windows see this site: Fix incorrect time in Windows + OSX dual boot

Not sure about Mac hardware but with x86 systems windows and Linux can change time/date in BIOS.

Yes, you set the time in BIOS, but it is interpreted differently in Windows and Mac OS. Windows is using the standard GMT (Greenwich Mean Time) to calculate your time zone, while Mac OS and Linux use the UTC. I haven't understood the exact difference, but apparently it is one hour off. So if you first boot into Mac OS or Linux and then into Windows your clock is one hour off since it is changed automatically in the other OS. One trick is to set the time manually and disable automatic change.

Thank you, spapakons! Spot on and problem solved - I would never have worked that one out in a thousand years!

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Been there, done that. Once I had installed a modified version of Mac OS X 10.8 Mountain Lion on my main PC (see 2nd system specs) on a spare disk. I too was surprised with the time issue.