How the Calendar Has Changed Over Time
We’re nearly halfway to the end of December, about to enter a “new year.” What does that mean, though? Why is January 1 considered to be the beginning of a new calendar year? Has it always been that way? How did the modern calendar come about?
The Earliest Attempts at Timekeeping
Historians and archeologists have conducted extensive research that suggests that human beings established methods of timekeeping and calendaring as early as the Neolithic Age (beginning around 10,000 BCE). The earliest timekeeping systems were generally based on the solar year (the time it takes for the sun to return to the same position in the sky), with the increments within the solar year revolving around the cycles of the moon and the unit of the day. Archeologists believe that a stone formation unearthed in Australia in 2000 may be a form of calendar dating back some 11,000 years. In 2013, they also found 12 pits in Warren Field in England, believed to represent the phases of the moon. Those pits were dated to approximately 8,000 BCE.
The Roman Calendar—The Introduction of an Algorithm
Before 45 BCE, a number of different calendars were developed and used, generally considered “lunisolar,” based on observations of the moon and sun. These included the Sumerian, Assyrian, Babylonian, Zoroastrian and Hebrew calendars. In the first century BCE, the Roman emperor Julius introduced an “algorithmic” calendar, based not on observations of the sun and moon, but on mathematical calculations. The new calendar, referred to as the “Julian” calendar, introduced a leap day every four years. It also changed the number of days in the various months, so that they did not coincide with the cycles of the moon. Under the Julian calendar, though, a year was still based on the amount of time it took for the sun to make its full circle.
The Gregorian Calendar—A Further Refinement of the Julian Calendar
According to the calculations used for the Julian calendar, each year had exactly 365.25 days. That’s why a leap day was added every fourth year. Initially, the leap day fell on February 24, which was celebrated for two consecutive days. It later became the 29th of February.
In the 16th century, scientists were able to confirm that the actual lunar year was longer (some 11 minute and change). The Gregorian calendar (named after Pope Gregory) in 1582. The driving factor behind the revision was the potential impact the Julian calendar would have on religious holidays, including Easter and Pentecost, and the fear that without the corrections, those holidays would eventually coincide with pagan holidays.
