Jill Wareham, age 11, of Spokane, Wash. for her question:

Who made the first calendar?

Early civilizations were farmers who needed to keep tabs on the changing seasons. So it was natural for scattered peoples to devise yearly calendars based on the seasonal motions of the heavenly bodies. Those early calendars were not very accurate, especially those based on the changeable moon. India, Egypt, China and Mesopotamia had calendars of some sort at the dawn of human history. Most likely the astronomers of ancient Mesopotamia made the first fairly good one, perhaps more than 6,000 years ago. This old timer allowed 12 months and 354 days for the average year  plus some special years having extra days and an extra month.