Today is February 28, the last day of this month… But not this year. Once every four years it is a leap year, a year where a day is added to February. Leap day, February 29. And this year it’s that time again, we get an extra day!
But why is that actually? We grabbed the calendar and got to work!
A leap year therefore has 366 days instead of 365. The introduction of this extra day has to do with something called the ‘tropical year’. And no, that is not a year in which all heat records are broken and heat wave follows heat wave.
The tropical year is the time it takes for the Earth to move from vernal equinox to vernal equinox in its orbit around the sun. The seasons are therefore fixed in the tropical year. And a tropical year is not exactly 365 days, but 5 hours, 48 minutes and 45.1814 seconds longer than that.
If you were to ignore that difference and round the duration of a year to 365 days, you would be almost one day short after four years. To be precise, you will be 23 hours and 15 minutes short. The result is that New Year’s Eve would then be celebrated too early, almost a whole day before the earth has actually completed a complete circuit around the sun.
The seasons would shift slightly on the calendar with each year, and the start of spring would begin about 24 days earlier every 100 years. Extend that over a few hundred years and we could eventually call winter summer!
That is why a leap day is needed, once every four years. But how do we know when we have that leap day? In our calendar, which we use in the Netherlands (it is called the Gregorian calendar), the leap day falls on February 29, and occurs when the year is divisible by 4, but not by 100. Unless the year is divisible by 400 without remainder. .
Sound complicated? Beats. In practice it looks like this: 2020 was a leap year. Before that, 2004, 2008, 2012 and 2016 (all divisible by 4, but not by 100) were also leap years. 1600 (divisible by 400) was also a leap year. 1700, 1800 and 1900 were not (divisible by 100, but not by 400) and 2000 was. And now it’s 2024, which is divisible by 4.
But why do we call it a leap year? Does it scare us sometimes?
The first part of leap year and leap month is indeed derived from the verb to scare, but from the outdated meaning. In the fourteenth century, to scare meant ‘to jump up, to take a big step or leap’.
A leap year is actually a year that takes a big step or jumps. This also corresponds to the English name leap year, literally ‘spring year’. From the original meaning of jumping to be frightened came ‘to jump up in fear, to recoil’ and finally ‘to become suddenly frightened’.
But where did that l suddenly come from in leap year? According to the Institute for the Dutch Language, it is like this: in the Middle Ages it was more common for compounds to be connected with the meaningless syllable -el. As for example in werkeldag (‘working day’), resteldag (‘rest day’) and sitteldag (‘day of the hearing’). We still use a few of these old constructions today, including Vastelavond (‘Shrove Tuesday’), SchortelWednesday (‘the Wednesday before Easter’) and of course leap year.
This year you have an extra day to submit your questions to Find Out!. You can do this below, or if it does not fit on the form or if you want to send photos, for example, [email protected].