The Calendar: The Link Between Agriculture and Astronomy
Astronomy and agriculture developed hand-in-hand from the time of late pre-history, launching us into the present epoch of historical civilization around 3000 BC. The regular motions of the sun, moon, planets, and stars were recorded for several millennia until the perfected measure of days, months, and years became a predictable and reliable science. The scale, precision, and human effort required to build and operate for example Stonehenge (ca. 2600 BC) clearly demonstrate the vital importance our ancestors placed on astronomy.
Stonehenge in Spring
Inventing astronomical calendars allowed our ancestors to plan the annual agricultural effort with far greater accuracy than ever before and maximize crop yields. The results were vast surpluses of food nearly every year, allowing art, music, poetry, and monumental architecture to flourish. As agriculture and our society advanced the calendar evolved as well, with increasing degrees of accuracy, until 45 BC, when Julius Caesar instituted the standardized 365-and-a-quarter-day solar year that still forms the basis of our calendar today.
The Julian Calendar