Emperor and pope gave us leap year
Leap day is the perfect time to get airborne.
February 29th, 2012
12:38 PM ET

Emperor and pope gave us leap year

It's leap day, a once-every-four-years bonus you can thank Julius Caesar and Pope Gregory XIII for.

We add a day at the end of February every four years because it takes the Earth about 365.242 days to make a full orbit around the sun. So we take those .242 days, round 'em up slightly and present the world with February 29, an extra day of, well, work for me, campaigning for the GOP presidential hopefuls or, if you fancy yourself a CNN iReporter, leaping!

Open Story: Leap day around the world

We thank the Roman emperor Caesar and the 16th century pontiff for putting the day into place.

In 46 B.C., Caesar decreed that under the Julian calendar, a day would be added in any year evenly divisible by four. However, accounting for the rounding up, that got the Romans a little ahead of themselves as far as time goes,  according to no less of an authority on things involving watches and calendars than timeanddate.com.

That little discrepancy, which amounted to 11 minutes every year, had added up to 10 whole days by 1582, when Pope Gregory said he had no time for inaccuracies and created the Gregorian calendar, under which we mark our days to this day. Gregory also designated February 29 as the official leap day and set up some rules so that we'd never end up 10 days ahead of ourselves again.

Here's how that works: Leap year occurs in every year that is evenly divisible by four and every century year that is divisible by 400. Hence, while 1200 and 2000 were leap years, 1700 and 1900 were not.

This also means that in the United States, leap years are presidential election years, which means we can always look forward to that extra day of campaigning.

Four million people born on leap day

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Filed under: Earth • History • Science
soundoff (67 Responses)
  1. Leucadia Bob


    February 29, 2012 at 3:52 pm | Report abuse |
  2. Leucadia Bob


    February 29, 2012 at 3:52 pm | Report abuse |
    • Ladislav Nemec Big Bear California

      You are technically correct. Caeser's name, however, became in many European languages the word for emperor. Not in Englishorn French but in German (Kaiser), Russian (Czar) and my tiny Czech language (cisar).

      So, while Gaius Julius Ceasar was NOT an emperor, he remains the great daddy of all emperors named, in a way, after him.

      When one deals with astronomy, one has to be precise. BTW, how we have a big controversy about leap seconds. US wants them Europeans do not. Or vice versa.

      What about Jews and Muslims who use internally lunar months completely out of sync with the earth orbit?

      And some thing calendars are trivial.

      February 29, 2012 at 6:31 pm | Report abuse |
  3. Gilbert Keller

    In 44 BC, Julius Ceasar was named dictator for life but Julius Ceasar was never an emperor. Augustus is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.

    February 29, 2012 at 4:05 pm | Report abuse |
    • JAB

      Thanks Gilbert –

      I was about to note the same thing.


      February 29, 2012 at 4:28 pm | Report abuse |
    • Gradivus

      As many have noted, Julius Caesar was never an Emperor. CNN isn't very good at fact checking. This is just a minor example, but their fact checking is lax in "hard" news stories as well. And their grammar isn't very good either. They're better than Associated Press in those things, but that's not saying much, to put it mildly.

      March 1, 2012 at 9:50 am | Report abuse |
  4. Leucadia Bob


    February 29, 2012 at 4:06 pm | Report abuse |
  5. C Glover


    February 29, 2012 at 4:17 pm | Report abuse |
    • Will Davis

      beat me to it.

      February 29, 2012 at 4:27 pm | Report abuse |
    • Timodeus

      Beat me too...

      February 29, 2012 at 5:49 pm | Report abuse |
  6. Zizewitz

    A further inaccuracy of the article, by stating:
    ""set up some rules so that we'd NEVER end up 10 days ahead of ourselves again".

    Each 1600 years, the Gregorian calender adds leap-year days (1600/4 – 12) = 388 days,
    which means (388/1600) = 0.2425 days per year, so taking care of a 365.2425 days year.

    But the astronomical real year has about 365.2424 days, so the gregorian calender ovecompensates 0.0001 days a year, so we will be in 3612 about 0.00001 x 1600 = 0.16 days out of sync referred to 2012, and to correct this we would nead to scrap 1 day somehere each 10,000 yers. them somewhere.

    If we do not do so, after about 16,000 years we would be again wrong by 10 days, this time in the opposite direction, which would really concern me greatly !!!

    February 29, 2012 at 4:26 pm | Report abuse |
    • D

      We will have already destroyed every living thing on this planet via WW3 or 4 so no worries about that one

      February 29, 2012 at 6:08 pm | Report abuse |
  7. Jerry Breen

    Don't you have the leap century thing wrong? As I recall, the year 2000 was NOT a leap year, although I was expecting it to be one. Isn't the rule that every 4th year (coinciding with U.S. Presidential elections years as well as Summer Olympic years) is a leap year with a February 29th, but every 4th century, you drop the leap year, which occurred in the years 1600 and 2000?

    February 29, 2012 at 4:43 pm | Report abuse |
  8. Jerry Breen

    Well, I know you have one thing wrong with regard to the "Century Year" detail. Since Pope Gregory formulated his revised calendar in the 1500's, the year 1200 could not possibly have been a "Century Year on his calendar. Duh!

    February 29, 2012 at 4:47 pm | Report abuse |
  9. banasy©

    Lets get back to the speculation of the chick in the picture.
    That was more fun.

    February 29, 2012 at 4:57 pm | Report abuse |
    • BOMBO ©

      I've come to the conclusion she's a shameless attention getter.

      March 1, 2012 at 12:12 am | Report abuse |
  10. Rat

    wow...does anybody really care? And if you do...well, how sad...so very very sad...

    February 29, 2012 at 6:16 pm | Report abuse |
  11. Dave

    When I was in grade school one of the kids in may class was born on Feb 29th, Leap Year. He would take great pleasure in pronouncing the fact that instead of being 12 years old, he was only 3. Ronnie Mitchell was his name. Yes I still remember you Ronnie at least every leap year. Hope your well.

    February 29, 2012 at 6:23 pm | Report abuse |
  12. Mark

    The roman calendar didn't have a year system that would even make the assertion made in this article make sense. Roman years were numbered according to the year of the proconsul's term under the democratic system, and the year of the emporer's rule otherwise.

    February 29, 2012 at 6:26 pm | Report abuse |
  13. Sergey

    How about state holiday today?
    It is n extra unaccounted day it should belong to people not to business!

    February 29, 2012 at 6:34 pm | Report abuse |
  14. 1608

    This year is my city's 41 st birthday. It's not that I care it's just something I think is crazy.

    February 29, 2012 at 9:16 pm | Report abuse |
  15. Sue

    The author states: "This also means that in the United States, leap years are presidential election years, which means we can always look forward to that extra day of campaigning"
    Wrong. 1900 WASan election year, and not a Leap Year, because it wasn't evenly divisible by 400. Furthermore, 2100 will ALSO be an election year but not a Leap Year (provided the Christian extremists haven't taken over, put a cross and spire on the White House, and banned elections) – because it is not evenly divisible by 400 -so please edit this article accordingly.

    March 1, 2012 at 11:01 am | Report abuse |
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