Leap year 2020: Why there is not February 29 every year

In the leap year 2020 there is one more day. But why is there only February 29th in the calendar every four years? The view of the sky explains it.

• Leap years are one day longer than so-called "common years" : they have 366 days
• 2020 is a leap year - this year leap day children can celebrate their birthday on February 29th
• There is a simple formula to determine a leap year

The year 2020 is a leap year , it has one day more than normal years: 366. To understand why this is so, you have to take a short trip to astronomy : A year is the time that the earth needs to to circle the sun once. But it doesn't exactly need 365 days, but 365 days, five hours, 48 ​​minutes and 46 seconds. So the so-called solar year lasts almost six hours longer than a normal year.

If there were not an additional leap day every four years (with a few exceptions), our time would deviate by almost six hours from astronomical reality over the course of a year. Almost a day comes together within four years. This day is offset by an additional day - February 29th.

Calculate leap year: This formula is used to determine when there is a leap day

However, a leap day is not inserted every fourth year - there are exceptions. If every fourth year were a leap year , the average year would be 365.25 days long and thus somewhat longer than a solar year. For this reason, three leap years fail in 400 years. To find out which year is a leap year , you can use the following formula :

• the year must be divisible by 4
• it must not be divisible by 100 - otherwise it is not a leap year
• Exception: if the year is divisible by 100 and by 400, then it is a leap year

The past leap years were the years 2008, 2012 and 2016. After the leap year 2020 the leap years 2024, 2028 and 2032 follow.

Born in the leap year - when do you celebrate a birthday when there is no February 29?

Around 55,000 people in Germany and around five million people worldwide should be particularly happy about the leap year 2020 : their birthday is on February 29 . Together with prominent leap day children * such as Dana Schweiger or Lena Gercke , they are faced with the question almost every year when they will celebrate their birthday: on February 28 or March 1?

In some cases, however, it is important to have legal regulations as to when the new age applies. For example, when is someone of legal age who has a birthday on February 29? This is regulated in paragraph 188 of the Civil Code (BGB): From a legal point of view, you are of legal age from March 1st.

The history of the leap year - from the Julian to the Gregorian calendar

The Julian calendar was introduced by Gaius Julius Caesar in 45 BC. He already took into account that the earth needs a little more than 365 days to circle the sun once: in the Julian calendar, a leap day was introduced every four years. As a result, the Julian calendar was too fast - exactly 11 minutes and 14 seconds per year.

Is an Office 365 license also included on February 29 in the leap year 2020? Or is there an Office 366 variant? # Office365

But even such apparently small deviations can add up: By 1582, the calendar had shifted by more than ten days. The day-and-night match, which was actually scheduled for March 21, fell to March 10, 1582.

Leap year: Pope Gregory XIII brought the calendar back in time

Pope Gregory XIII remedied this: in 1582 he struck ten days from October (after October 4, October 15 came directly) and thus got the calendar back on track. Pope Gregory XIII. determined that three leap years will be missed in 400 years - otherwise the calendar would have shifted again in the long term. The Gregorian calendar has been in effect since 1582 and still fits very well today: the average year is 365.2425 days, just a few seconds too short for astronomical reality.

By Tanja Banner

* fr.de is part of the nationwide Ippen-Digital central editorial office.

List of rubric lists: © picture alliance / dpa / Lukas Schulze