The Gregorian calendar is the international civil calendar used worldwide. Introduced in 1582 by Pope Gregory XIII, it corrected the drift of the Julian calendar and better aligned the calendar with the solar year. Today it is the global standard for business, government, and daily life.
The Gregorian calendar replaced the Julian calendar in 1582 because the older system added too many leap years, causing a drift of about 10 days over centuries. Adoption was gradual, with Catholic countries switching first and others joining over time.
The Gregorian calendar has 12 months and 365 days in a common year. A leap year adds one day every four years, except in years divisible by 100 unless also divisible by 400. This keeps the calendar in sync with Earth's orbit around the Sun.
To correct inaccuracies in the Julian calendar and ensure Easter and other holidays stayed aligned with the seasons.
Nearly every country in the world uses the Gregorian calendar for official and civil purposes.
The Julian calendar, introduced by Julius Caesar in 46 BCE, was used in Europe before being replaced by the Gregorian reform.