Many factors can interfere with the Earth's rotation, which could change the lenght of a day.
New research has discovered the Earth's core can change a say's length by milliseconds.
Three-hundred million years ago, a year lasted 450 days and a day 21 hours. As the years go by the Earth's rotation slows down, increasing the length of day, a University of Liverpool press release reported.
The Earth's rotation on its axis can be affected by other things. Winds blasting against mountain ranges can change adds a millisecond to the day, or take it away over the course of a year.
Richard Holme, a Liverpool School of Environmental Sciences professor, looked at the fluctuations in day length from 1962 to 2012.
The study told all time-altering factors into account to build a model of how time has changed over the past few decades.
"Previously these changes were poorly characterised; the study shows they can be explained by just two key signals, a steady 5.9 year oscillation and episodic jumps which occur at the same time as abrupt changes in the Earth's magnetic field, generated in the Earth's core," Holmes said.
"This study changes fundamentally our understanding of short-period dynamics of the Earth's fluid core. It leads us to conclude that the Earth's lower mantle, which sits above the Earth's outer core, is a poor conductor of electricity giving us new insight into the chemistry and mineralogy of the Earth's deep interior," he said.
In 2009 the Antarctic Circumpolar Current (a strong ocean current) slowed down drastically for two weeks, NewScientist reported.
Researchers noticed as soon as the current slowed down the Earth's rotation sped up, which shortened the day by 0.1 milliseconds. The days returned to normal as soon as the current did.
This was the first time scientists had seen a change in current strong enough to affect the Earth's rotation.
Winds in the area that were moving in the same direction as the current slowed down too, but researchers said it was unusual to see such a strong effect on the ocean.
