The United States Naval Observatory (USNO) ... CO which, with the "Master Clock", provides precise time to the GPS satellite constellation run by the U.S. Air Force; ...

The beep and the blip are both wired into the US Master Clock, so they really are simultaneous. ... So the Naval Observatory—which was in Foggy Bottom then—erected a huge brass-colored orb on its roof ...

Precise Time is kept in the U.S. by the Navy, at the U.S. Naval Observatory in Washington, D.C. The history of that dates back to a horrible tragedy at sea more than 300 years ago.

This corresponds to 6:59:59 pm Eastern Standard Time, when the extra second will be inserted at the U.S. Naval Observatory's Master Clock Facility in Washington, DC. Skip to main content Your ...