The 28 fastest days on record all occurred in 2020, with Earth completing its rotations around its axis milliseconds quicker than average, scientists said. The shortest day was July 19, when Earth completed one spin 1.4602 milliseconds faster than 86,400 seconds. Before 2020, the shortest day was noted on July 5, 2005, when the Earth's rotation was 1.0516 milliseconds faster.