A Gregorian calendar is a calendar system based on the 365-day common year and the leap year that is used in most of the world today. The Gregorian calendar was introduced in 1582 and was developed by Pope Gregory XIII to replace the Julian calendar, which had been in use since 45 BCE. It is based on the solar year, with each year having 365 days, except in a leap year, when there is an extra day. The Gregorian calendar is a solar calendar, meaning it is based on the position of the sun, and it is a reformed version of the Julian calendar. It is used by most countries in the world and is the most commonly used calendar in business and government.
