Calenders have been developed over centuries in order to better understand natural cicles and design life inline with the natural patters.
it is a great example of "Observe and interact". During the development of human coltures societies have developed Calenders that make life easier to manage, and understand.
Cultures created holidays to celebrate Harvest, and to come celebrate the light in the darkest phase of the year. when farmers observed the passing of seassons and madea adjustments and improvements to gain higher yeld and better prepare their soils, theirs livestock and house.