The action -- scheduled to occur at 00:59 July 1 British Summer Time -- is required since Earth does not rotate at a constant speed, whereas atomic clocks, including several at Britain's National Physical Laboratory, are much better at keeping time.
Due to the unpredictable nature of Earth's movement, leap seconds are occasionally required to bring atomic time back into alignment with astronomical time, ensuring that on average the sun remains overhead at noon, an NPL release said Friday.
"The Earth is a poor timekeeper compared to our clocks, and its rotation changes unpredictably due to changes in its atmosphere and molten core," said Peter Whibberley, Senior Research Scientist in NPL's Time and Frequency Group. "The purpose of leap seconds is to make sure our time scale based on atomic clocks remains in step with the time based on the Earth's rotation.
"The leap second correction to our atomic clocks means we get an extra second of summer time," he said.