A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. The Gregorian calendar is the most widely used calendar in the world today. It was introduced in 1582 by Pope Gregory XIII as a reform of the Julian calendar. The Julian calendar had been in use for over 1,600 years, but it had become inaccurate because it was not synchronized with the Earth’s orbit around the sun.
The Gregorian calendar is a solar calendar, which means that it is based on the Earth’s orbit around the sun. The year in the Gregorian calendar is divided into 12 months, each of which has either 30 or 31 days. The only exception is February, which has 28 days in a common year and 29 days in a leap year. Leap years occur every four years, except for years that are divisible by 100 but not by 400.
