So, we shall have one second in The Thirty-first of June (1961) as J. B. Priestley said.

International timekeepers are adding a second to the clock at midnight universal time Saturday, June 30, going into July 1. Universal time will be 11:59:59 and then the unusual reading of 11:59:60 before it hits midnight.

http://www.usatoday.com/tech/science...day/55923680/1