Calendar

The Gregorian calendar spread through European colonialism and later through international relations, exchange, and commerce. It developed from the first-century B.C.E. Julian calendar, named after Julius Caesar, who commissioned its development and approved the reckoning of months no longer determined by lunar observations in a year that averaged 365.25 days. The Gregorian gets its name from Pope Gregory XIII, by whose election in the year 1572 C.E. the day marking the vernal equinox had strayed ten days from its occurrence. His papal bull in 1582 set out the mechanisms by which:

1. the spring equinox would occur on its actual date;
2. Easter—which depends on calculations from the vernal equinox—would be determined; and
3. a leap year system would be implemented, allowing for prolonged congruency between the calendar and its astronomical underpinnings.

Since the sixteenth century, countries around the world have adopted the Gregorian calendar, including its twelve fixed months, seven-day weeks, and beginning date. However, day and month names usually occur in the vernacular, and traditional reckonings may be kept for local, ethnic, and religious observances.

Through calendars, humans impose culturally significant rhythms on the perception of time. Across human cultures two primary perceptions of the character of time predominate:

1. time as recursive or cyclic, observed in the recurrence of day and night, lunar waxing and waning, and the return of the seasons; and
2. time as linear, an ongoing process, observed in the maturation of vegetation, decay, and the transition of a human life from birth to death.

Specially marked dates and periodicities are the human, cultural cadence in the infinitude of time. While unable to control the passage of time, humans with calendars have increasingly ordered their relationship to and utilization of it.