The most interesting thing about Göbekli Tepe the oldest megalith structure discovered, is that a study based on the drawings on the structure correlated with Younger Dryas period might explain why nothing was found about the ancient civilization that built it.
Hmm... Seems very speculative. I think you'd need some more evidence before concluding this is a calendar that you can interpret.
That said, the entire site is of interest to those interested in flood myths. It was an active site during the period when climactic disasters and floods were happening. Ice melted. Seas rose. The nearby black sea was expanding, and eventually spilled into the aegean. This is also (intriguingly) the date plato gave for atlantis' destruction.
https://phys.org/news/2017-04-ancient-stone-pillars-clues-co...
https://www.newscientist.com/article/2128512-ancient-carving...
Science might just have found the cause for the flood myth that is present in most cultures around the world.