Leap Second Added in 2008 To Counteract Earth’s Slowing Rotation

Sarah Knapton, Telegraph: A ‘leap second’ will be added onto the final minute of 2008 because the planet is gradually slowing down as it spins on its axis. The tweak will help correct the time-lag which shows up on ultra-accurate atomic clocks.

It is the 24th time since 1972 that the adjustment has been made by the Paris based International Earth Rotation and Reference Systems Service at intervals varying from six months to seven years. The last was in 2005.

Historically, time was based on the rotation of the Earth relative to celestial bodies. Earth’s trip around the sun is about 365.2422 days long, which we round down to 365. Every four years, during a leap year, the inaccuracy is corrected by adding a day in February.

World commerce and digital technology depend on accurate to-the-second timekeeping. Mechanisms such as the Internet-based Network Time Protocol and the satellite-based Global Positioning System (GPS) depend on the accurate time kept by atomic clocks.

That extra second will make 2008 — already long with an extra day on Feb 29 — the longest year since 1992.