The USNO websites,,,,, and are undergoing modernization efforts. The expected completion of the work and return of service is estimated as 30 April 2020. Please submit a requirements form to the USNOPAO if the information you are seeking is not accessible via other means.

Frodsham Clock

This clock was made by Charles Frodsham of London (1810-1871) and purchased by the Naval Observatory in April 1848 for $420. It was used as the observing clock for the prime vertical instrument in the South Wing of the old Naval Observatory at 23rd and E Streets, N.W. until 1882.
USNO Master Clock Time
Javascript must be Enabled