Cannot Synchronize Internet Time

Everytime I click the UPDATE NOW button in a Date & Time Control Panel in order to synchronize my Internet Time with Internet Time Servers, an error occuredwith an errors message "AN ERROR OCCURED GETTING THE STATUS OF THE LAST SYNCHRONIZATION. THE rpc SERVER IS UNAVAILABLE".  What must be done to avoid this error and synchronize my Internet Time with the such servers successfully?  I had already tried all the Internet Time Servers in the computer but still unsuccessful. I had brought this case to the Technical Support via email through 'support.euro.dell.com' a week ago and had made a follow-up last Monday but until now I haven't heard from them.