What Calendar Do We Use Today?
We are currently using the Gregorian calendar, at least most of us on the planet are, not that there’s anything wrong with any other calendar, the Gregorian calendar is just the most widely used calendar today. It is derived from the Julian calendar and named after Pope Gregory XIII who decreed the new calendar on February 24th 1582.
The years in the Gregorian calendar continue from the Julia calendar which began from the traditional birth year of Jesus, the ‘anno Domini’ (AD) era, sometimes referred to today as the ‘common era’ (CE).
The change occurred to correct the Julian calendar which was slightly too long and consequently Easter was slowly drifting forward in the calendar. The solution was the addition of the leap year and the subtraction of ten days from the Julian calendar. The leap year rule states:
Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100; the centurial years that are exactly divisible by 400 are still leap years. For example, the year 1900 is not a leap year; the year 2000 is a leap year.