2009 will arrive one second late

Everyone who is eager to see the back end of 2008 be forewarned the worlds official timekeeper is prolonging the year by one full second.

The International Earth Rotation and Reference Systems Service (IERS) in Paris, mandated the extra second.

The change is necessary because satellites that orbit at speeds calculated in kilometers (miles) per second, the Internet, global positioning systems -- all depend on knowing exactly what time it is.

IERS head Daniel Gambis announced the time-stretching measure in July in a letter addressed to "authorities responsible for the measurement and distribution of time".

These folks are the guardians of the 200-odd ultra-accurate atomic clocks scattered around the globe.

The last adjustment was in 2005, and the next could happen in 2012 or 2013.

Leap days occur once every four years because it takes 365 days plus six hours for the planet to complete an orbit around the Sun. But leap seconds are added strictly on a case-by-case basis, depending on need.

This year's added second will be the 24th bonus second since the practice of adding time began in 1972.

The addition of time is necessary to reconcile two different time scales. One is established by the atomic timepieces, which are accurate to a billionth of a second per day. The other is based on the Earth's imperfect rotation on its own axis.

The two get out of sync because the planet's spin is affected by a host of fluctuating variables, including the movement of the tides, solar wind, magnetic storms, space dust, and solar and lunar gravity. Even melting ice caps have an impact.

And so, at exactly 23:59:59 Greenwich Mean Time (GMT) -- or Coordinated Universal Time (UTC) on December 31, the world's clocks will add a beat.