History of the Calendar
The purpose of the calendar is to reckon past or future time, to show how many days until a certain event takes place—the harvest or a religious festival—or how long since something important happened. The earliest calendars must have been strongly influenced by the geographical location of the people who made them. In colder countries, the concept of the year was determined by the seasons, specifically by the end of winter. But in warmer countries, where the seasons are less pronounced, the Moon became the basic unit for time reckoning; an old Jewish book says that “the Moon was created for the counting of the days.”
Most of the oldest calendars were lunar calendars, based on the time interval from one new moon to the next—a so-called lunation. But even in a warm climate there are annual events that pay no attention to the phases of the Moon. In some areas it was a rainy season; in Egypt it was the annual flooding of the Nile River. The calendar had to account for these yearly events as well.
- History of the Lunar Calendar
- History of the Egytpian Calendar
- History of the Roman (Julian) Calendar
- History of the Gregorian Calendar
- Adoption of the Gregorian Calendar