A Leap Second
So the world isn't perfect. No big news there. In fact, it is so imperfect that it doesn't travel as fast as it did yesterday. To compensate for the Earth's mediocracy, we have added a leap second at the end of the year. This isn't an uncommon thing; the last one was in 2005. Unlike leap years, however, they don't come at regular intervals.
Cherish your leap second, you never know when the next one will creep up on you. Where will you be for yours?