Damn I missed it!
However, this would seem to be an admirable opportunity to re-publicise the following:
If you feel inclined to get seriously geeky about the Metonic Cycle, here's a page from my website on which I preserved an almost dangerously long article on the subject of the Metonic Cycle, and its relationship with Stonehenge, that I wrote in 2001:
http://www.ringmerlewes.freeserve.co.uk/CURSUSWALKER/the%20metonic%20cycle.htm
Best of luck!