How Accurate Is the Gregorian Calendar, Based on the Leap Year Algorithm?

How accurate is the Gregorian calendar?

In a timespan of 3236 of years the Gregorian calendar shifts 1 extra day in error over to the astronomical one. The approximate error in the previous Julian calendar: 1 day every 128 years. Details below...

Following the Gregorian reform, the average calendar year length is now 365,2425 days, an even better approximation to the astronomical year (≈ 365.242216).

At this rate, it takes about 3236 years for the Gregorian calendar to get into errors, gaining 1 extra day versus the astronomical year, from the moment of its creation in 1582.

By then though we'll probably come up with another better calendar, in advance real time computer synchronized with the astronomical year, based on real time measurements.

Every calendar is just an approximation.

To make a calendar a better measurement of the astronomical year, determined by the Earth's orbit around the Sun, leap year rules were created and have since been improved. These improvements have resulted in a better synchronization between the calendar year and the astronomical one, but the calendar year will only be an approximation:

  • The approximate error in the Gregorian calendar: 1 day every 3236 years.
  • The approximate error in the previous Julian calendar: 1 day every 128 years.

Articles on the leap years

1. What is a leap year? What is a common year?

2. How often do the leap years occur in the calendar?

3. Why do we need leap years?

4. Leap years algorithm. Examples.

5. When did the actual concept of the leap year originate?

6. The modern (Gregorian) calendar and the Julian one. Julian calendar adjustment

7. How accurate is the Gregorian calendar, based on the leap year algorithm?

List of all the leap years between 1582 and 4818.

Leap years calculator. Is it a leap year or a common one?