For use with Windows based servers, there is a slight workaround to get the clocks to sync.
You will need to install our software called TimeSync onto a Windows 7 or newer PC/Server (do not install TimeSync on your domain controller).
Set TimeSync to use the NTP server as its time source. You can do this by clicking Add on the Main tab, select NTP Server as the protocol and specify the IP address of the time server.
Navigate to the 'NTP Server' tab of the software and enable this feature by clicking the checkbox and setting the slider to 'Stratum 2'. Then navigate back to the 'Main' tab and apply the settings.
In the config of the clocks, set the time source to be the IP Address of the PC/Server with TimeSync installed. Check the other settings are as you want them and then save the settings and reboot the clock.
Once this is done, the clocks should now remain synchronised.
If you require TimeSync, please submit a support ticket here and we will assist you.
TimeSync V4 Manual: http://support.galsys.co.uk/index.php?/Knowledgebase/Article/View/35/0/timesync-4-manual