A one-second correction that may be applied to atomic time to align it more closely with Universal Time, compensating for changes in the Earth's rotation. Since the first correction was made in 1972, all leap seconds have been positive, reflecting the general slowing of the Earth's rotation due to tidal braking. See also UTC. For more detailed information, including a list of all leap second corrections made to date, see http://tycho.usno.navy.mil/leapsec.html.
a second (see second, Systeme International) added between 60s and 0s at announced times to keep UTC within 0.90 s of UT1. Generally, leap seconds are added at the end of June or December.
a second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation
an adjustment to UTC by skipping or adding an extra second on the last second of a UTC month
an intercalary Intercalation is the insertion of an extra day, week or month into some calendar years to make the calendar follow the seasons
a one-second adjustment that is used to keep civil time aligned with the Earth's rotation
UTC (Coordinated Universal Time) is computed by occasionally adding leap seconds to International Atomic Time (TAI). Since 1972, these leap seconds have been added on December 31 or June 30 at the rate of about one every 18 months.
A leap second is an intercalary, one-second adjustment that keeps broadcast standards for time of day close to mean solar time. Leap seconds are used to keep time standards synchronized with civil calendars, the basis of which is astronomical.