Keeping time, it turns out, is a messy business. In order to satisfy science, religion, and sometimes ego, our calendar has changed quite a bit throughout history. This video by Jeremiah Warren tells the story up to now.
Since we can’t predict what changes might be made in the future, the 10,000 Year Clock has been designed to keep track of the cycles of the Sun, the Moon, the planets and the constellations – things even the largest of egos will have trouble changing.