(We all know about leap years, which occur once every four years because it takes 365 days plus six hours for our planet to complete an orbit around the Sun, but seemingly leap seconds are added on a strictly at need basis, because satellites orbit at speeds calculated in miles per second, and the Internet, (GPS) global positioning systems etc all need to know exactly what time it is.
So the countdown to 2009 went something like this: "...3, 2, 1 and a half, 1... Happy New Year!")