Problem with time

[Macintyre]

I have installed Yosemite on my PC and I also have Windows 7 and 10 pro dual booted on another drive. I have noticed that after using Yosemite, when I go back to Windows, the system time is one hour early. I have to reset the system time every time I go back to Windows after using Yosemite.

The obvious solution of course is not to go back to using Windows.....

However, I was wondering why this is happening and whether there is a workround?

Thanks.

 

[RehabMan]

I have installed Yosemite on my PC and I also have Windows 7 and 10 pro dual booted on another drive. I have noticed that after using Yosemite, when I go back to Windows, the system time is one hour early. I have to reset the system time every time I go back to Windows after using Yosemite.

The obvious solution of course is not to go back to using Windows.....

However, I was wondering why this is happening and whether there is a workround?

Thanks.

Search google for 'RealTimeIsUniversal Windows registry'.

 

[Macintyre]

RehabMan, thank you for that. I did a search on that as you suggested. Most interesting. This link seemed to contain a good writeup on the subject:

https://www.cl.cam.ac.uk/~mgk25/mswish/ut-rtc.html

So it seem that Windows is the odd one out here running the RTC in local time rather than real time as do other operating systems. So why doesn't the opposite happen, i.e when I set the time forward one hour in Windows, why doesn't OSX then show the time as one hour forward?

 

[Macintyre]

As a further note to this, there seemed to be some conflicting information about whether this registry setting should be used or not and warnings of possible other problems in Windows. So was there another approach?

When you boot into OSX after setting your time in Windows an hour forward to get back to the correct time and then boot into OSX, OSX does not show the time advanced by an hour, but still shows the correct time. I think the reason for this is because OSX uses a proper NTP server for its time source and automatically corrects the time from where Windows left it on boot up. So it ocurred to me to take the same approach in Windows. Instead of using the Windows time service, why not install a proper NTP service instead?

I downloaded and installed and set up the NTP software from Meinber here:

https://www.meinbergglobal.com/english/sw/ntp.htm#ntp_stable

Now when I go back to Windows, the NTP service automatically sychronises the time to what it should be just as OSX does.

 

[RehabMan]

...
So it seem that Windows is the odd one out here running the RTC in local time

Not really. Ubuntu default is local. The choice is arbitrary with system RTC as GMT the slightly better choice. Windows and other systems use local time as a historic artifact.

So why doesn't the opposite happen, i.e when I set the time forward one hour in Windows, why doesn't OSX then show the time as one hour forward?

OS X will sync to the internet time server more often, perhaps on boot.

 

[Macintyre]

Not really. Ubuntu default is local. The choice is arbitrary with system RTC as GMT the slightly better choice. Windows and other systems use local time as a historic artifact.

I understand that Ubuntu originally used UTC but changed this to local time in order to resolve this dual booting with Windows time issue. Some argue that the BIOS clock should always be set to UTC and the OS should use UTC as the reference and not attempt to set the BIOS clock to local time.

OS X will sync to the internet time server more often, perhaps on boot.

Agreed. It would appear that Windows time only checks about once a week and evidently not on boot so that when OSX resets the BIOS clock to UTC, Windows then uses the UTC time as local time rather than calculating the proper offset from UTC. Using a proper NTP service means that time is synchronised on startup just like in OSX and is thereafter periodically checked to keep time in sync. The only problem with this solution is that the BIOS clock is reset between each switch of the OS but so long as I am seeing the correct system time, does it really matter?

Incidentally I see Windows 10 has the same issue so I will try the same solution on there. I am a bit wary of using an unsupported registry key.