When:
June 30, 2017 all-day
2017-06-30T00:00:00-06:00
2017-07-01T00:00:00-06:00
Where:
http://www.timeanddate.com/time/leapseconds.html
June 30. This day is one of the times that has been favored forthe addition or subtraction of a second from our clock time to coordinate atomic and astronomical time. The determination to adjust is made by the International Earth Rotation Service of the International Bureau of Weights and Measures, at Paris, France.