Your Linux system will generally have two clocks, a hardware clock/real time clock (RTC) and a system clock.
The hardware clock is physically present and continues to run from battery power even if the system is not plugged into a power source, this is how the time stays in place when there is no power available.
You could automatically add a NTP server to the next update of Slide OS config until this bug is tracked down. The Country and time zone are set correctly in the International settings.
The 1500 series DVRs are able to automatically adjust the date and time if they have a connection to the internet or to a local time server if you are operating one. We recommend that you use your router's IP address as the primary and the Google public DNS as the secondary (fallback).
Aside from that, to ensure that your clock stays in sync when you're traveling, tick the box next to the "Detect time zone" option.
I can sync time of win7 from a ntp linux server manually.
That's strange, but it's possible that it didn't get correctly set at configuration time...
This is a minor problem for Kodi/Slide OS if you set up the ntp server in openele settings.
But if you want to run something else in Slide, it may be a problem.