The 30th of June will quite literally be the longest day of the year.
It is because that day will witness a rare clock phenomenon - the leap second.
No, the time 23:59:59 will not be the last second of the day in June 30th. We are being made for the arrival of July. Those of you who are alert enough will witness the clock flash up the number 23:59:60.
The leap second was introduced in 1972 and accounts for irregularities in the earth's rotation of the earth. Essentially, the earth rotates around the Sun at varying speeds. Therefore, leap seconds are only scheduled six months in advance.
The last one occurred on the same day (June 30th) in 2012.
The big question now is - What are you going to do with your leap second?