Leap Seconds
To keep the civil day aligned with the apparent movement of the Sun, positive or negative leap seconds may be inserted.
A civil clock day is typically 86,400 SI seconds long, but will be 86,401 s or 86,399 s long in the event of a leap second.
Leap seconds are announced in advance by the International Earth Rotation and Reference Systems Service which measures the Earth's rotation and determines whether a leap second is necessary. Leap seconds occur only at the end of a UTC month, and have only ever been inserted at the end of June 30 or December 31.
Read more about this topic: Day
Famous quotes containing the words leap and/or seconds:
“O thou day o’ th’ world,
Chain mine armed neck, leap thou, attire and all,
Through proof of harness to my heart, and there
Ride on the pants triumphing!”
—William Shakespeare (1564–1616)
“Watching fifteen seconds of nasal passages unblocking sure beats watching thirty seconds.”
—Barbara Lippert, U.S. advertising critic. As quoted in Newsweek magazine, p. 8 (June 16, 1986)