Mayan calendar
The Mayan calendar was a sophisticated calendar used by Earth's ancient Mayans.
In the ancient past, a being known as Kukulkan gave the Mayan civilization a remarkably accurate calendar, according to which the Mayans were supposed to build a city according to its cycles. After the city was finished, Kukulkan was supposed to return, so the Mayans built their city and waited; however, Kukulkan never appeared. (TAS: "How Sharper Than a Serpent's Tooth")