Why did the Sumerians create the calendar

The Sumerian Calendar and the Sumerian system of irrigation were both connected by one thing; farming. Both these inventions made farming easier for the Sumerians.

Explanation:

Based on their observations, they invented a calendar which had 12 months and each month had around 30 days. The days of a month would start and end at sunset. Each day had 12 hours, 6 hours of daylight and 6 hours of night.

answer; migrate from a region;

just don't strip down in public lol