A calendar is a system of organizing days for social, religious, commercial, or administrative purposes. The most common type of calendar is the Gregorian calendar, which is used in most of the world today. The Gregorian calendar has 12 months, with January and February being the first and second months, respectively.
January has 31 days and February has 28 days, except in leap years when February has 29 days. Leap years occur every four years, except for years that are divisible by 100 but not by 400. For example, the year 2000 was a leap year, but the year 1900 was not. The Gregorian calendar is based on the Earth’s orbit around the sun. It takes the Earth approximately 365.25 days to orbit the sun. To account for this fraction of a day, the Gregorian calendar adds an extra day to February every four years.
