Dictionary.com

Why Do We Have Leap Year?

leap

Even though the standard calendar year is 365 days, the Earth actually takes 365 days 5 hours 48 minutes and 46 seconds to go completely around the sun. (This is called a solar year.) In order to keep the calendar cycle synchronized with the seasons, one extra day is (usually) added every four years as February 29th.

The Julian calendar (established by Julius Caesar in 46 BCE) introduced the Egyptian solar calendar to the Roman world, standardized the 365-day year, and created the predecessor to our current leap year. February 29th was not reflected on the Julian calendar, rather February 23 was repeated every four years.

You may be asking, “The solar year is not a full 365 days and 6 hours, so what about those extra 11 minutes and 14 seconds?” An additional calendar reformation in the 1500s added a special rule to adjust for this discrepancy. In 1582 Pope Gregory XIII created a slightly modified calendar to better account for leap days. Called the Gregorian calendar, this new system said that no century year (like 1900) would be a leap year except for centuries divisible by 400 (like 2000). In order to correct the calendar, the Pope eliminated October 5 through October 14, 1582. The calendar moved directly from the fourth to the fifteenth to align the dates with the seasons again. It feels almost like science fiction to think that ten full days were removed from the calendar in the year 1582.

But where does the phrase leap year come from?

In 365-day years, known as common years, fixed dates advance one day in the week per year. For example, Christmas fell on a Thursday in 2014 and on a Friday in 2015. With the insertion of a leap day, dates (following February) advance two days instead of one. In 2016, Christmas will leap over Saturday to fall on a Sunday.

Will you be celebrating leap day in anyway?

75 Comments

  1. Keith Anker -  April 2, 2016 - 12:32 am

    “Will you be celebrating leap day in anyway?
    Oops! “any way”

    Reply
    • timmy -  April 6, 2016 - 9:54 am

      hi nice article

      Reply
  2. Raxin -  March 30, 2016 - 4:21 pm

    The last sentence of the article has a typo: “Will you be celebrating leap day in anyway?” should be, “Will you be celebrating leap day in any way?”

    Leap seconds are cool too. They’re added sporadically as needed.

    Reply
  3. scott -  March 13, 2016 - 8:13 pm

    If time didn’t exist until the 18th century how did the Egyptian/Romans know that the year was slightly longer and to repeat February 23rd?

    Reply
  4. Bobby Licker -  March 8, 2016 - 12:28 pm

    Nice and interesting article. :)

    Reply
    • Leap_Year_Baby -  March 17, 2016 - 6:13 pm

      I know right! P.S. I was born on leap year 2004

      Reply
    • Horses girl -  March 28, 2016 - 5:02 pm

      I no right

      Reply
  5. E. K. Y. ABREFAH -  March 1, 2016 - 2:15 am

    Our world is ruled by the powerful, Gregory, Junius have through their invention imparted our minds and even decision.

    Reply
  6. julianna -  February 29, 2016 - 8:00 pm

    It is nine days not ten. Get your math right.

    Reply
    • Charlie -  March 3, 2016 - 2:43 am

      October 5 through October 14 is 10 days, not 9. (“through” = inclusive of)

      Reply
      • jack johnson -  March 8, 2016 - 8:15 pm

        ayyyyyyyyyyyyyyyy lmao

        Reply
    • old -  March 6, 2016 - 8:33 pm

      It IS ten : the 5th thru the 14th inclusive.YOU get your math right.

      Reply
      • allie -  March 10, 2016 - 3:13 pm

        noo

        Reply
    • anonymous -  March 18, 2016 - 8:28 am

      It is 10 days. jumped from 4th to 15th, that is, 5th, 6th, 7th, 8th, 9th, 10th, 11th, 12th, 13th and 14th.

      Reply
  7. Gus -  February 29, 2016 - 5:50 am

    I disagree with the definition of leap year.
    It should be every year that is divisible by 4, except if it is divisible by 100, but one exception to that is if it is also divisible by 400.

    1800 : not a leap year
    1900: not a leap year
    2000: leap year

    Reply
    • alyssa holden -  March 1, 2016 - 12:45 pm

      NOOOOOOOo u have it all wrong leap year is agin in 2020

      Reply
      • b -  March 4, 2016 - 9:09 am

        i think you are corect 2016+4 years=2020

        Reply
        • Person -  March 5, 2016 - 8:09 am

          Leap years:
          2016
          2020
          2024
          2028
          2032
          2036
          2040

          Reply
          • uhb -  March 9, 2016 - 11:39 am

            Hey, summer olympics on same year

  8. Richard -  February 25, 2016 - 3:45 pm

    I was born on March 1, 1957. I’ll be celebrating my 59th birthday on Tuesday, of the following week; and the only regret I have is that my immediate families are an ocean away, in West Africa but that won’t stop the fun! And, thank God my lovely Mother had me before February 29! Otherwise, I would be celebrating most of my birthdays on February 28, each common year and would technically be about 47+ years old by now.
    Meantime, thank God to live thus far and to be in a well-toned healthy shape. Go March 1!

    Reply
    • Geraldine -  February 28, 2016 - 9:55 am

      I love the fact that you Thanked God. My Birthday is March 8. Thank God I was created. Amen. God Bless you on your day. May God grant you all the desires of your heart. Happy Birthday in advance.

      Reply
      • katrina -  March 7, 2016 - 8:58 pm

        its your day..happy bday.

        Reply
    • KKellyOB -  February 29, 2016 - 11:25 am

      If your birthday is March 1st how were you born before February 29th? And if you were born on February 29th and you would be about 47+ now, then you would be about 188 now?

      Reply
      • Jumeriah -  March 1, 2016 - 5:29 pm

        Wait?!?! What do you mean?! you are confusing me right now?

        Reply
        • Sandra -  March 3, 2016 - 7:46 am

          Maybe he meant he wasn’t born during a leap year.

          Reply
    • Jumeriah -  March 1, 2016 - 5:22 pm

      HAPPY BIRTHDAY!

      Reply
    • nael -  March 5, 2016 - 11:21 am

      your birthday is the same as my sister except not 1957

      Reply
  9. Hanna Sane -  April 9, 2013 - 9:14 pm

    Today, I went to the beach front with my children. I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She put the shell to her ear and screamed. There was a hermit crab inside and it pinched her ear. She never wants to go back! LoL I know this is completely off topic but I had to tell someone!

    Reply
    • Madison -  February 29, 2016 - 6:42 am

      A guy at my church is celebrating his 15 the birth day

      Reply
      • Madison -  February 29, 2016 - 6:43 am

        He is actually 60 but is 15

        LOL

        Reply
    • Sandra -  March 3, 2016 - 7:53 am

      Poor baby girl. Mom, you should always inspect anything that you pick up off of the ground. Stuff that you pick up from the ground 101!

      Reply
    • nael -  March 5, 2016 - 11:23 am

      is her ear okay?

      Reply
  10. El Gato -  February 29, 2012 - 2:32 pm

    How about sidereal days? Did you know that the rotation of the earth through 360 degrees is a sidereal day and not a regular (solar) day? This is because during a solar day, the earth has moved in its orbit a bit and so must turn a few degrees beyond 360 in order to have the sun above the same spot on the earth. A sidereal day uses a remote star as the reference point.

    Reply
    • kenneth torret -  February 28, 2016 - 1:55 pm

      Your story is beautiful though.

      Reply
  11. euroangel -  February 28, 2012 - 2:04 pm

    my friend was born on a leap year..she celebrates her birthday every 28 of february..thanks for this info here.

    Reply
    • bobby -  February 29, 2016 - 7:18 am

      who cares

      Reply
    • Jumeriah -  March 1, 2016 - 5:24 pm

      I have a friend that was born on a leap day the doctors wanted to make it on March 1st but his birth was urgent!
      Cool though and also sad!

      Reply
  12. Fat Boy -  May 11, 2011 - 6:06 pm

    yes it is!!!!!!!!!!!!!!!!

    Reply
  13. Fat Boy -  March 15, 2011 - 2:28 pm

    wow jace that is random but cherub is AWESOME!!!!!!!!!!!!!!

    Reply
    • fatboy -  February 29, 2016 - 7:19 am

      sup

      Reply
  14. wordjunkie -  March 1, 2011 - 4:14 pm

    um….Nate? The year 2000 was a leap year.

    Reply
  15. Jace -  March 1, 2011 - 8:13 am

    read CHERUB

    Reply
  16. Fat Boy -  March 1, 2011 - 8:12 am

    I’m awesome because my birthday is on feb29th

    Reply
    • sam will -  February 28, 2016 - 5:55 pm

      no no your not flab boy

      Reply
  17. ... -  March 1, 2011 - 2:33 am

    i think if you birthday is on feb 29 you just celebrate it on the 28 when its not leap year

    Reply
  18. random 9th grader! -  February 28, 2011 - 1:32 pm

    This is interesting. I’m not really the type that likes stuff like this but this was very informative. I like articles like this! And my baby neice was born in 2000… But if someone was born tomorrow, would that make them a leaper?

    Reply
  19. nate -  February 28, 2011 - 1:18 pm

    How ’bout telling the world WHY the year 2000 was not a leap year??

    Reply
    • Bod Owens -  February 28, 2016 - 8:23 pm

      Um, actually, they did. In the article, it CLEARLY states that according to the Gregorian calendar, “no century year (like 1900) would be a leap year except for centuries divisible by 400 (like 2000)”. For someone on a dictionary website, you sure aren’t great at reading.

      Reply
    • Conrad -  February 29, 2016 - 6:03 am

      Uh, Master Nate – 2000 WAS a leap year. On planet Earth, that is!!

      Reply
  20. Joseph -  February 28, 2011 - 11:54 am

    To Mr.Anderson: The Mayan calender does not predict the end of life. It is only the sick-minded that say that. I hope you are not one of them. Scholars who know the Mayan hieroglyphs say that there is no end predicted there. The calender basically ends there, but the Maya did not build an infinite calender.
    I would like to learn more about the Mayan calender.

    Reply
    • random 8th grader -  February 29, 2016 - 6:18 pm

      well, in reality the mayan calender restarts after each cycle.

      Reply
  21. Ray -  February 28, 2011 - 11:49 am

    1. RE: Ashley on February 28, 2011 at 1:33 am

    You might– celebrate at exactly the stroke of midnight, so that your party falls between Feb. 28th and Mar. 1st., and only 29′ers would have the right time…!

    2. RE: D Williamson on February 28, 2011 at 7:12 am

    Once upon a time, 365.2425 days/year was correct– ca the era of Adam and Eve, But– the Earth’s rotation also slowly slows, so it’s no longer so correct…!

    (But, should we suppose that Pope Gregory XIII actually knew this slight fact…?)

    3. And for the digitally inclined, Notice also that, had we a binary calendar, we’d have more accuracy yet– as, 365 + (1/4) – (1/128) = 365.24219, right-on today!

    (That’s 1 0110 1101.0011 1110 days/year in fixed-point-Binary representation.)
    __

    REF: The slowing of Earth rotation is attributed to lunar tidal-drag, (which must mean sea level on an east coast is slightly higher than on a west coast, but this does not change mass-weight-constancy at sea level, around the world), at the rate of 5-6 msec-per-year per year, or 60-70 μ-day-per-year per millennium….

    Reply
  22. astro -  February 28, 2011 - 10:38 am

    Technically, the next leap-day is one revolution around the sun (one earth year) away, not one solar rotation (~25 days) away.

    Reply
  23. Maddi -  February 28, 2011 - 9:26 am

    i was born on a leap year. Did u know that most people born in leap years are smarter than those who are not?

    (all of this was a LIE) (I hatien you)

    Reply
  24. Jace -  February 28, 2011 - 7:49 am

    Interesting!

    And as I understand, leap year rules are -slightly- more complicated.

    If the year is evenly divisible by 4 – you have leap year.
    UNLESS
    The year is evenly divisible by 100, then NO leap year
    UNLESS
    The year is evenly divisible by 1000, then you DO have a leap year

    Thus, 2012 IS a leap year, 1900 was Not, but 2000 WAS.

    Reply
  25. D Williamson -  February 28, 2011 - 7:12 am

    Years that are evenly divisible by 100 are not leap years, unless they are also evenly divisible by 400, in which case they are leap years. For example, 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Similarly, 2100, 2200, 2300, 2500, 2600, 2700, 2900 and 3000 will not be leap years, but 2400 and 2800 will be. By this rule, the average number of days per year will be 365 + 1/4 − 1/100 + 1/400 = 365.2425, which is 365 days, 5 hours, 49 minutes, and 12 seconds. – from Wikipedia

    Reply
  26. Liza with a Z -  February 28, 2011 - 6:27 am

    If February 29 is the day when woman can propose marriage to a man, does that means it’s also known as Sadie Hawkins Day?

    Reply
    • Kate -  March 4, 2016 - 9:09 am

      When I was growing up, February 29th was considered Sadie Hawkins Day and Dog Patch Day! There were always fun activities, such as the school Sadie Hawkins dance where girls could ask boys to be their dates; girls could also propose marriage on that day (this was back in the day when that was the ONLY appropriate day for girls to be so bold). The day was special at home, at school, and in the community.

      Reply
  27. MOOT -  February 28, 2011 - 5:30 am

    If Dogpatch Day fell on 29 Feb the guys wouldn’t have a chance.

    Reply
  28. meleagrid -  February 28, 2011 - 2:28 am

    By the Metonic cycle, this year is a leap year. Those who depend on the supposedly more accurate lunar calendar would agree with that. An extra month is added at certain intervals and in 19 year cycles to produce a calendar where the dates always are supposed to be the same day. For example, if one was be born on a Saturday, that person would always celebrate the birthday on a Saturday the same time of the year every year. Calendars and time they measure are rather complex, but over the centuries they have been refined. Too really find why this came about and why it so, read more about. It’s all in the math. Wikipedia, of course, has a pretty good discussion.

    Reply
  29. thabo andrew mpheqeke -  February 28, 2011 - 1:41 am

    somewhat abtract.somhow interesting and mind-boggling, but it’s astronomy where time is the central focus. come up with more articles of this nature.

    Reply
  30. Ashley -  February 28, 2011 - 1:33 am

    Hi. My name is Ashley. Dictionary.com, I really like your post. Pretty cool. My friend Kylie was born on Feb 29, 2000. Technically she’s only two. But we still celebrate her birthday on the 28th if it’s not a leap year. This article is so awesome because now I can call her a leaper! Yay! Cool! Actually I think today is the 28th…yeah that’s right! I celebrated Kylie’s sort-of birthday today…we had some cake! I can’t wait till next year…Kylie will be “three”! But we still count her as eleven. I really like her. And I really like your article, Dictionary.com! Thanks for sharing. Especially since it finally has nothing to do with Spain!

    Bye for now
    –Ashley :)

    PS Pinch and a punch for the last day of the month

    Reply
    • Sky the Hedgehog -  March 14, 2016 - 7:06 pm

      What’s wrong with Spain?

      Reply
  31. Lucia -  February 28, 2011 - 1:18 am

    Hm, but the article is not exactly correct. Leap years that end a century happen only every 400 years. That is, 2000 was a leap year and 2100 will be not, the next secular leap year will be 2400. That’s because the time lost every 365 days is not exactly 6 hours… that would be too easy!

    Reply
  32. Mr.Anderson -  February 28, 2011 - 1:06 am

    Very good artical !But just wanted to know did the miayian calender also have leap years if not how could they predict that life as we know it would end in 2012 ???????

    Reply
  33. TrulyMe -  February 27, 2011 - 7:31 pm

    The revised Bangla calendar mimics the Gregorian one? I never knew.

    Reply
  34. TrulyMe -  February 27, 2011 - 7:30 pm

    LOL. Nice article. That was one smart five year old! :P

    Reply
  35. ivorybrunette -  February 27, 2011 - 6:26 pm

    Guess I’m the first. The only thing I have to say is that for all I’ve been hearing lately about the “wide-ly held tradition” of a woman proposing to a man on a leap day, I had never known about this not too long ago. Can anyone tell me when this started and how?

    Reply
  36. Eyewitness -  February 27, 2011 - 5:59 pm

    Leapin’ Lizards! You mean February 29th isn’t an orphan?

    Reply
  37. Ray -  February 27, 2011 - 5:46 pm

    That’s all fine-and-dandy for those who live in Romanized countries… But in the Grecized countries they do a bit differently– the semiofficial Orthodox calendar since 1924, replaced the 400th-rule by more-accurate 200th-or-600th-modulo-900…. However, we shouldn’t-need worry about this until A.D. 2800….

    Ray.

    * Rumania (Romania) is purportedly included with the Greek, despite its name.

    REF: http://adsabs.harvard.edu/full/1946MNSSA…5….6B

    Reply
  38. Jane -  February 27, 2011 - 5:29 pm

    I love this post. My FIL was born on 29 February but I always understood him to be a ‘leapling’, not a ‘leaper’. Have you heard of that one?

    Reply
  39. Bob -  February 27, 2011 - 5:09 pm

    woah that’s very interesting but next time state the actual fact that was proposed in the title, THEN go on to related facts please!!!

    Reply
  40. Steve Osuman -  February 27, 2011 - 4:34 pm

    This is a nice piece of knowledge. I now know why 29february is called a leap day and those born on such days are called ‘leapers’.

    Reply
  41. Queen Sardonic -  February 27, 2011 - 2:46 pm

    YES! An article NOT about Spain. I mean, I love Spanish as much as the next person, but one can only take so much Espanol.

    I loved this article! Keep up the good work!

    Reply

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