The extra second, or "leap second," is needed to resynchronise our land-based clocks with Earth's rotation, which is slowing down ever so slightly each year, it said.

This is the 26th time a second has been added to the day since the practice began in 1972.

Due to tidal forces between the Earth and the Moon, our planet's rotation is slowing down, adding a whopping 1.4 milliseconds to our days every century. However, 1.4 milliseconds add up over time.

During the time of the dinosaurs, the typical day on Earth was just 23 hours.

In fact, the last true 24-hour rotation, exactly 86,400 seconds, occurred in 1820.

Since then, the day has lengthened by 2.5 milliseconds, according to NASA.

We have these precise measurements, thanks to punctual NASA scientists who have been monitoring Earth's rotation using a technique called Very Long Baseline Interferometry (VLBI), the report said.

The last leap second, in 2012, caused a mayhem on popular websites with clocks synced to standard civil time.

In a bid to avoid this, Google added a millisecond of time to their servers with each update so they were caught up with the new time when the leap second occurred.