Many people will remember 2020. For example, the 28 fastest days on record since 1960 occurred in the last year. The Earth very often completes a revolution on its axis milliseconds faster than usual. This is not particularly alarming – the planet’s rotation changes slightly all the time, due to fluctuations in atmospheric pressure, winds, ocean currents and the movement of the core.
This is really important for timekeepers who keep track of time accuracy.
Adjustments usually consist of adding a leap second towards the end of the year. The earth has typically slowed down since 1960, so scientists added leap seconds in June or December every 18 months. The last time it was in 2016.
The acceleration of the Earth’s rotation in 2020 has raised the debate about negative leap seconds. It looks like scientists may soon need to subtract one because the average day length is 86,400 seconds, but the astronomical day in 2021 will be 0.05 milliseconds shorter on average. Over the course of a year, this will lead to a lag in atomic time of 19 milliseconds. It is possible that scientists will completely abandon leap seconds if the Earth continues to accelerate its rotation.
In 2020, the shortest day was July 5th. The Earth has completed a revolution 1.0516 milliseconds faster than the standard 86,400 seconds.