Answer:
Sumerian astronomers tracked movements of the stars, planets and the
Moon. Based on their observations, they invented a calendar which had 12 months and each month had around 30 days. Therefore, altogether, 12 months had 360 days. This was the first concept of years, months and days.
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Explanation: SUMERIAN CALENDAR
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. However, this calendar was not always completely accurate and every 4 years or so, the Sumerians inserted a extra month to the calendar.
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