There might be a problem if you have a domain controller that is NTP server for the domain. The server might not update the time from external NTP server, even if you added an existing NTP server from the internet. There is a simple reason for that. By default windows is configured to update time from internet but there is a registry key that is not set correctly to effectively update the time from this server.
First go to:
in the key NtpServer you can set your preferred NTP server in the internet. For example pool.ntp.org
Then go to:
find the key called Type and change it’s value to NTP
After adjusting these keys open cmd and run the following command:
net stop w32time && net start w32time
The system time should change within the next few minutes.
All that is described in a Microsoft KB article: KB816042