Why is it called a “leap year”?


According to the Oxford English Dictionary, “leap year” means “a year, occurring once every four years, that has 366 days including February 29 as an intercalary* day.” Where did the “leap” come from?

The OED goes on to explain that it comes from late Middle English: “probably from the fact that feast days after February in such a year fell two days later than in the previous year, rather than one day later as in other years, and could be said to have “leaped” a day.”

So to take an example: Christmas Day fell on a Wednesday in 2013, on Thursday in 2014, and on Friday in 2015. But because 2016 is a leap year, Christmas will “leap” a day to Sunday this year.

Happy February 29.

* intercalary: “(of a day or a month) inserted in the calendar to harmonize it with the solar year, e.g., February 29 in leap years.” (OED)

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