Since I was checking the Wikipedia article anyway (for when the last leap second was inserted), it also has an answer for this: "Because the Earth's rotational

Since I was checking the Wikipedia article anyway (for when the last leap second was inserted), it also has an answer for this: "Because the Earth's rotational speed varies in response to climatic and geological events, UTC leap seconds are irregularly spaced and not precisely predictable." https://en.wikipedia.org/wiki/Leap_second https://en.wikipedia.org/wiki/Leap_second