A recent summer has seen a few specific days on Earth’s spin being slightly faster than usual, resulting in minor variations in the length of time. Scientists track these phenomena, but they are not concerned about the changes. According to Christian Bizouard, an astronomer at the Paris Observatory, “It’s a very small phenomenon” and there is nothing extraordinary happening. The variation occurs on July 10, July 22, and August 5, with each day being approximately one thousandth of a second faster than the average over several decades.
Source: https://www.scientificamerican.com/article/why-earth-is-rotating-extra-fast-this-summer-shortening-days-by-milliseconds