Leap Year / Leap Day

Happy Leap Day 2012!

Quiz: In any ten year period, what's the minimum number of leap years? What's the maximum? (answer at bottom of page)

Leap Day the book, by Wendy Mass:
It's the story of soon-to-be-sixteen Josie Taylor who was born on Leap Day, February 29, and now it's her "fourth" birthday. Like any average teenager, sometimes she wonders what other people are thinking, but today it's the reader who gets to find out, by "leaping" into the minds and viewpoints of Josie and everyone around her. Birthday surprises, school play auditions, her driver's test, a scavenger hunt, and the all-important sweet-sixteen initiation at the lake—these are the things that define Josie Taylor today. But what defines her tomorrow and in the days to come are the people who touch her life at every moment. A fascinating, at times astonishing, new novel, Leap Day is full of everyday imaginations and truths in the life and future of one "everygirl" teenager.
See It's My Birthday... Finally! A Leap Year Story

Leap day (February 29) only occurs during a Leap Year.

Leap Year occurs every four years, except for years ending in 00, in which case only if the year is divisible by 400.

So what's the possible Y2K problem with Leap Day?:

Read the rule above again. If chipmakers and programmers got the rule perfectly correct, then there will be no problem. If they only used the main rule (every four years) but neither exception, then the year 2000 will show up as a leap year, and the only problems would be for those already using the year 2100 for some reason, but the impact in this case would be minimal. If for some reason, however, the chipmakers and/or programmers were to use the main rule (every four years) and only the first exception (except every hundred years) but not the second exception (except every four hundred years), then 2000 would come up as not being a leap year. Computers would then go from February 28 directly to March 1.

See also: Y2K Center on Alert for Leap Year Problems

Leap Day Links: (Scroll down for quotes and information)
  • Feb 30, 1712?
  • Calculate your Solar Year Birthday -- this site lets you calculate the date of the anniversary of your birth, defined as a rotation of the earth around the sun.
  • Leap Year Info
  • 2000 AD is a Leap Year
  • Leap Seconds
  • Leap Seconds and more Leap Seconds as explained by the US Naval Observatory
  • Worldwide Leap Year Festival is not an annual event! Festival History
  • DEC Answers Leap Year Complaint
  • Yahoo's Leap Day Page
  • John Strohsacker's Leap Day page (born on Leap Day, 1968!)
  • Origins of Roman Calendar

    From The Atlanta Journal-Constitution, December 29, 1995, p.2:

         Most years ending in "00" are not leap
    years, but those divisible by 400 (including 2000)
    are. The Julian calendar, authorized by Julius
    Caesar in 46 B.C., assumed that the year had
    365 1/4 days, with a 366-day leap year added
    every fourth year.
         In A.D. 730, an Anglo-Saxon monk, the Venerable
    Bede, calculated that the Julian year was 11 minutes
    and 14 seconds too long, an error of about one day
    every 128 years.  But nothing was done about it for
    800 years. In 1582, the accumulated error was
    estimated at 10 days, and Pope Gregory XIII decreed
    that the day following Oct. 4 would be Oct. 15.
         To make future adjustments for the error
    (about three days every 400 years), it was decided
    that years ending in "00" would be common years rather
    than leap years -- except those divisible by 400.
         So 1600 was a leap year and 2000 also will be,
    but 1700, 1800 and 1900 were not.

    Bissextile. The day which is added every fourth year to the month of February, in order to make the year agree with the course of the sun.

    Leap year, consisting of 366 days, and happening every fourth year, by the addition of a day in the month of February, which in that year consists of twenty-nine days.

    By statute 21 Hen. III., the 28th and 29th of February count together as one day. This statute is in force in some of the United States. Porter v. Holloway, 43 Ind. 35; Harker v. Addis, 4 Pa. 515. (Black's Law Dictionary, Fourth Edition, 1951).

    The New York Times, January 5, 1995:
    "Wait a Second ... That Was a Leap Day!"
    To the Editor:
    In your Dec. 31 issue, two references are made to the "leap second" that 
    was to be added to the last hour of 1995. One was in the Week in Review 
    section, the other in the magazine column by James Gleick. Both draw an 
    analogy between the periodic addition of a second at the end of a year 
    to the insertion of an extra day in leap yers.
    The re appears to be a logical disconnect in the use of the term "leap 
    second" and linking it to the term "leap year." The additon of an extra 
    day to the calendar once in a four years defines a leap year, not a leap 
    day, week or month. 
    Linguistic consistency demands, therefore, that the additional second 
    added at the end of the year not be referred to as a leap second nor 
    lend the "leap" designation to the last minute or hour but rather to the 
    last day. Dec. 31, 1995, should be called a leap day.
    Jacob E. Goldman
    Westport, Conn., Jan. 2, 1996

    Quiz answers:
    Since January 7, 1996, The Web-Counter counts this many visits:
    MAPILab.Com - Home of must have Outlook add-ins

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