Powerful currents around Antarctica caused the earth to spin slightly faster in November 2009 - by about 0.1 milliseconds.
The Antacrtic Circumpolar Current rings in the continent slowed down around 8 November 2009, but sped back up around two weeks later.
The changes caused the earth to spin faster, but the earth’s speed, along with the current returned to normal on 20 November 2009.
This is the first time scientists have observed a rapid change in oceans strong enough to impact the earth’s rotation.
Read more at NASA, Institute of Earth Physics of Paris