Olli

I've played around with this issue in the past and it seems to be an ongoing challenge.  Each successive version of Windows locks the system down further and further and in general an application under Windows 10 is not expected to change the systemTime.  The application would need Administrator rights.

More specifically it needs SE_SYSTEMTIME_NAME privilege.  You can read more about it here.  
https://docs.microsoft.com/en-us/windows/desktop/api/sysinfoapi/nf-sysinfoapi-setsystemtime

The calling process must have the SE_SYSTEMTIME_NAME privilege. This privilege is disabled by default. TheSetSystemTime function enables the SE_SYSTEMTIME_NAME privilege before changing the system time and disables the privilege before returning. For more information, see Running with Special Privileges=16px.

I'd love if Nick could find a way to implement it reliably but I think it is simply too dependent on the Windows configuration.  If anyone has had any success with this on a recent version of Windows then maybe they could share with the group.