How to set time server for Windows server 2008, SBS2011 & 2012

Open the command prompt and type:

net stop w32time

Configure the external time sources, type:

w32tm /config /syncfromflags:manual /manualpeerlist:0.pool.ntp.org

Make your PDC a reliable time source for the clients. Type:

w32tm /config /reliable:yes

Start the w32time service:

net start w32time

The windows time service should begin synchronizing the time. ...
Check the Event Viewer for any errors.