I believe that it all depends upon what is considered to be a calendar.
Stonehenge, Woodhenge, medicine wheels, and other ancient constructions used to mark the passages of the sun, moon and stars are calendar devices of a sort. But they are also considered to be primitive observatories that duly mark the regular passages of the heavenly bodies.
Agriculture seemed to be the motivating factor in the need of the ancients to develop them. But then one may ask, how did they figure all of that stuff out? And how did this phenomenon demonstrate similarities and consistencies of construction attributes on a worldwide scale thousands of years ago?
flow....
