system clock not consistent in a dual boot system

Question

I am running Windows 7 and Ubuntu 17.04 Zesty version in a dual boot configuration. The problem I am facing is this: - The system clock shown in the two OS remains different (separated by 5 hours and 30 minutes).

I am actually in the Time Zone of south Asia (GMT+5:30). For example, if in Windows OS,I set the time as 00:00, as soon as I reboot the system and open Ubuntu,the system clock in Ubuntu starts to show 5:30. Similarly, setting 00:00 in Ubuntu OS shows +5:30 in Windows and so on. This happens for whatever time I set in any of the OS. The other OS starts to show the time that is +5:30 ahead.

Answer 1

This may be due to the fact that both systems are trying to mess with the hardware clock (the one set in your BIOS).

While Windows relies on setting the hardware time to your local time (GMT+5:30), Ubuntu relies on setting it to UTC, then configuring the system clock based on the hardware clock (UTC) and applying your timezone difference to it.

One solution (and the preferred one) is to let Ubuntu handle the hardware clock and do a registry trick in Windows in order to let it make use of UTC instead of localtime.

The alternative would be letting Windows manage the hardware clock while setting your Ubuntu install to use localtime and disabling any clock-updates services (like NTPd).

Answer 2

See Clock time is off on dual boot (on Ask Ubuntu).

The preferred solution is to have Linux accept the local time clock, since changing Windows ways appears unreliable.

man hwclock will tell you everything you want to know (and more) about the hardware clock and how it is managed.