Because the early 70’s, it has change into customary working process so as to add a leap second to account for the truth that astronomical time is 2.5ms slower than atomic time. In actual fact, between 1972 and 2016, a complete of 27 seconds have been added as the speed of the earth’s rotation slowed. Over time, that fee of slowing has, properly, slowed, and projections are exhibiting that the change in mass on the earth’s poles will push the necessity for a adverse leap-second correction as quickly as 2026.