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 is a solar calendar, meaning that it is based on the Earth’s orbit around the Sun. The Gregorian calendar has 12 months, with 28 days in February in a common year and 29 days in February in a leap year. Leap years occur every four years, except for years that are divisible by 100 but not by 400.
The Gregorian calendar was introduced in 1582 by Pope Gregory XIII. It replaced the Julian calendar, which had been in use since 45 BC. The Julian calendar was a solar calendar with 365 days in a common year and 366 days in a leap year. However, the Julian calendar was not as accurate as the Gregorian calendar, and it gradually drifted out of sync with the Sun. The Gregorian calendar is more accurate because it takes into account the fact that the Earth’s orbit around the Sun is not exactly 365 days long.
