Leap second: Difference between revisions

Revision as of 17:00, 10 February 2004

Revision as of 13:06, 29 February 2004

Line 1:

A '''leap second''' is a one-second adjustment to civil time in order to keep it close to the [[mean solar time]].

<table{| border="1" cellspacing="0" width="20%" cellpadding="2" alignstyle="float:right"; style="margin-left:15px;">

<tr><td |align=center>| '''List of leap seconds'''

|-

<tr><td>

|style="padding-right: 1.5em;"|

# [[1 July]] [[1972]]

# [[1 January]] [[1973]]

Line 26 ⟶ 27:

# [[1 July]] [[1997]]

# [[1 January]] [[1999]]

|}

</td></tr>

<tr><td></td></tr>

</table>

Civil clock time is based on [[UTC|"Coordinated Universal Time" (UTC)]], which is maintained by extremely precise [[atomic clock]]s. In contrast, the rotation of the Earth, measured by the [[UT1]] timescale, is irregular; the solar day is gradually but unevenly becoming longer, mainly due to the [[tidal acceleration]] of the [[Luna|Moon]]. In order to keep solar time close to civil time, UTC is corrected by a leap of 1 second.