Question

On what did the Mesopotamians and Egyptians base their calendars? *

Answer 1

The formula was probably invented in Mesopotamia in the 3rd millennium bce. ... The date of Easter ... As late as about 1070 bce, his installation date was not fixed in the calendar. ... The ancient Egyptians originally employed a calendar based upon the Moon, and, like many peoples throughout the world, they regulated

So basically,  The worlds creation