You can try
http://www.time.gov/ The official U.S. Time site
This public service is cooperatively provided by the two time agencies of United States: a Department of Commerce agency, the National Institute of Standards and Technology (NIST), and its military counterpart, the U. S. Naval Observatory (USNO). Readings from the clocks of these agencies contribute to world time, called Coordinated Universal Time (UTC). The time maintained by both agencies should never differ by more than 0.000 0001 seconds from UTC
This web site is intended as a time-of-day service only. It should not be used to measure frequency or time interval, nor should it be used to establish traceability to NIST or the USNO.
You can download software from NIST and theUSNO in order to use the Internet to automatically set your computer clock to the correct time.