This came about from a conversation with Nicholas Kollerstrom at the National Astronomy Meeting. Having worked on how Delphi’s oracle was timed, he suggested that I look into the Olympics. This seemed like it should be comparatively easy, not because you only have to explain one year in four, but because he more or less gave me the answer during the talk. The Olympics, he said, could be tied to the Venus cycle.
I should point out that if I had read the Da Vinci Code then I would have known this would be a dead end.