Question: how to configure an authoritative time server in windows server 2008 r2?
Answer: Change the server type to NTP. To do this, follow these steps: ... 
Set. ... 
Enable NTPServer. ... 
Specify the time sources. ... 
Select the poll interval. ... 
Configure the time correction settings. ... 
Close Registry Editor.
At the command prompt, type the following command to restart the Windows Time service, and then press Enter: