About

It was introduced by Pope Gregory XIII in 1582 as a reform of the Julian calendar, which had become out of sync with the solar year. The Gregorian calendar made several changes to the Julian calendar, including adjustments to the length of the year and the addition of leap years. These changes brought the calendar closer to the actual length of the solar year and improved the accuracy of the calculation of the date of Easter. The adoption of the Gregorian calendar varied across different countries, with Catholic countries being the first to adopt it. Protestant countries, however, resisted the change due to political and religious reasons. Eventually, though, most countries adopted the new calendar system. Today, the Gregorian calendar is the internationally accepted standard, used in virtually all countries for civil purposes and for determining religious holidays. It is a solar calendar with 365 days in a common year and 366 days in a leap year. The Gregorian calendar's accuracy in tracking the solar year, along with its widespread adoption, has made it the most widely used calendar system in the world.