Here's why June 30 will be one second longer

Washington: Strictly speaking, a day lasts 86,400 seconds. On June 30, the day will officially be a bit longer than usual because an extra second or "leap" second will be added and NASA has an explanation for this.   "The Earth's rotation is gradually slowing down a bit, so leap seconds are a way to account for that," said Daniel MacMillan, NASA's Goddard Space Flight Center in Greenbelt, Maryland.   This is the case according to the time standard that people use in their daily lives - Coordinated Universal Time or UTC.   UTC is "atomic time" -- the duration of one second is based on extremely predictable electromagnetic transitions in atoms of cesium.   These transitions are so reliable that the cesium clock is accurate to one second in 1,400,000 years.   However, the mean solar day -- the average length of a day, based on how long it takes the Earth to rotate -- is about 86,400.002 seconds long.   "That is because the Earth's rotat...