The Gregorian Calendar is the calendar system most widely used today. Introduced by Pope Gregory XIII in 1582, it was designed to correct inaccuracies in the previous Julian Calendar, which miscalculated the length of the solar year. The Gregorian Calendar has 12 months, with a total of 365 days in a common year and 366 days in a leap year, ensuring that the seasons align properly over time. This calendar is essential for organizing our daily lives, scheduling events, and planning holidays. It also plays a significant role in various cultures and religions, influencing celebrations like Christmas and New Year's Day.