Leap Second Came And Went
The transition from June to July will be delayed by circumstances beyond everyone's control. Time will stand still for one second on Saturday evening (June 30) because a "leap second" will be added to let a lagging Earth catch up to super-accurate clocks.
International Atomic Time is a very accurate and stable time scale. It is a weighted average of the time kept by about 200 atomic clocks in over 50 national laboratories worldwide. Atomic time is measured through vibrations of atoms in a metal isotope that resembles mercury and can keep time to within a tenth of a billionth of a second per day. The result is extremely accurate time that can be used to improve synchronization in precision navigation and positioning systems, telecommunications networks and deep-space communications.