Leap Day: 29 Facts and Figures

Little Critters 2016 wall calendar by Amber Lotus

Image by Kate Endle from our Little Critters 2016 wall calendar. Click image for more info.

    1. Leap Days don’t actually occur every 4 years. They occur in years that are divisible by 4, but they do not occur in years that are divisible by 100 unless the year is also divisible by 400. This means that the years 1700, 1800, and 1900 were not leap years; 2000 was; 2100, 2200, and 2300 will not be; and so on.
    2. The reason to add the occasional Leap Day is because the tropical year (the amount of time the Earth actually takes to orbit the sun) is not exactly 365 days.
    3. A tropical year is 365 days, 5 hours, 48 minutes, and (about) 46 seconds.
    4. Julius Caesar first introduced Leap Days in approximately 46 BCE with his Julian calendar, which added a Leap Day every 4 years.
    5. But this was an overcompensation that had added up to about 10 days by 1582, when Pope Gregory XIII recalibrated the calendar to rectify the problem of a wandering Easter. His Gregorian calendar is the one we use today.
    6. Catholic countries followed suit and adopted Pope Gregory’s calendar. But not all countries were as quick to submit to the power of the Church. For example, Russia didn’t switch over until 1918 and Greece waited till 1923, by which time they had to skip over 13 days in order to calibrate to the new system.
    7. Since many countries were slow to adopt the Gregorian calendar, the Leap Day of 2000 was special in that it was the first to fulfill the “divisible by 400” rule for the majority of the world.
    8. In Sweden and Finland, 2 days were added to February in 1712 – February 29 and 30 – to synchronize their calendar with their neighbors’.
    9. Our calendar is still not perfect: it overcompensates by about 3 hours every 400 years.
    10. This means we add one whole day about every 3,200 years.
    11. Without Leap Days at all, we would lose almost 6 hours each year.
    12. This would add up to about 24 days over 100 years.
    13. Over 400 years, this would add up to more than 96 days lost, which would put us one whole season behind.
    14. A Leap Day occurs once every 1,461 days, meaning the chance of having February 29 as a birthday is 1 in 1,461.
    15. People born on a Leap Day are referred to as leaplings or leapers.
    16. The Honor Society of Leap Year Day Babies has more than 10,000 members worldwide.
    17. The Guinness Book of Records lists only one family – the Keoghs of Ireland – that has produced three consecutive generations of leaplings.
    18. The world record for the number of siblings born on February 29 was originally held by the Henriksen family of Norway, with three siblings born on consecutive Leap Days in 1960, 1964, and 1968.
    19. This record has recently been tied by the Estes family of Utah, whose children were born on Leap Days in 2004, 2008, and 2012. If they have another child today, they’ll move the record to 4.
    20. It is estimated that there are about 4.1 million leaplings worldwide.
    21. Many countries have laws that govern the day on which a leapling is considered to have reached each age. For example, in New Zealand a leapling’s official birthday is on February 28, whereas in the United Kingdom the official date is March 1.
    22. The twin cities of Anthony, Texas, and Anthony, New Mexico, have declared themselves to be the Leap Year Capital of the World. The cities hold a four-day festival, which includes a huge leapling birthday bash.
    23. James Milne Wilson, the eighth premier of Tasmania, Australia, was born on the Leap Day of 1812 and died on the Leap Day of 1880.
    24. The Scots consider it unlucky for a person to be born on a Leap Day.
    25. The Greeks consider it unlucky for a couple to marry on any day of a leap year, but particularly on the Leap Day itself.
    26. In some European countries during the Middle Ages, a man refusing a woman’s wedding proposal on a Leap Day was expected to buy her 12 pairs of gloves (presumably so she could hide the “shame” of not having an engagement ring).
    27. February 29 is Saint Oswald’s Day, which commemorates the death of the archbishop of York. His day is celebrated on February 28 during common years (those with 365 days).
    28. Fittingly, Rare Disease Day is acknowledged on February 29.
    29. The term “leap” year refers to the fact that, while fixed-day holidays advance by one weekday each year, the added Leap Day causes these holidays to “leap” over a weekday. (Let’s take Saint Patrick’s Day for example, on March 17: 2013 it was on a Sunday, 2014 a Monday, 2015 a Tuesday, but it will “leap over” Wednesday this year and be on a Thursday.)

Tanya FoxOriginally from Australia, Tanya Fox spent several years living and working in Germany, where she happened to meet a nice young man from Oregon. She ended up moving to Portland to marry him, where they now live with their two children. She works as a freelance editor, proofreader, writer, and translator, and delights in the wide variety her work brings her. She can be contacted for publishing projects.

 

 


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And here’s more on this day of mathematical curiosities from the every enlightening and charming Neil deGrasse Tyson:

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