Hello February 29: This is why we have leap years

Happy leap day 2024! Typically the year has just 365 days so why does 2024 have this extra day, February 29th?

The reason? Earth orbits the Sun in an average of 365 days, five hours, 48 minutes and 45 seconds. However, a calendar year lasts 365 days, creating a deficit. To compensate for this, there is a leap year every four years. However, this still does not perfectly capture the orbit around the sun.

To further refine our calendar, every 100 years we skip a leap day unless that year is divisible by 400, like the year 2000. This puts our calendar slightly ahead of actual solar time, which is noticeable in the shifting start dates of the seasons.

From 2048, the astronomical start of spring will take place on 19 March. In 2100, a leap year will be skipped, so that from 2102 the start of spring will once again fall on March 21.

The different seasons are determined by the inclination of the earth's axis to the Sun's orbit. Until now, the Sun has been exactly at its zenith at the equator on March 20 or 21. In the coming years, it will usually be March 20 and later also March 19.

Therefore, leap years are essential for maintaining our regular seasonal weather conditions in the long-term.

Meteorological spring officially begins on March 1, check back tomorrow to celebrate its arrival and learn more on why there is a difference.