For TimeHack you have to enable Java/JavaSkript and when you are behind a firewall, you have to open Port 8013 for ip 132.163.4.203 for outgoing TCP [time.gov].

If you want to set the clock on your computer to an exact time,  try AboutTime, it's freeware for MSWindows.  For europe insert as time-host: ptbtime1.ptb.de