i know how you are really frustered with all these numbers so here it is in plain english and then scientifically
every year is actually 365.25 days long, so in order to ensure that our calendar doesn't get thrown off over time, we just give February an extra day once every 4 years.it takes the earth 365 and one quarter days to orbit the sun. So on the fourth year we gain a day
here is the math: every year is about 365.25 days so you add 25+25+25+25 ( the quarter ) and you get 366 days this only happens every 4 years.
now here it is more scientifically:
Our solar year (the time required for Earth to travel once around the Sun) is 365.24219 days.
Our calendar year is either 365 days in non leap years or 366 days in leap years (Feb 29th inserted).
A leap year every 4 years gives us 365.25 days, sending our seasons off course and eventually in the wrong months.
To change .25 days to .24219, we need to skip a few leap days (Feb 29ths) .... century marks not divisible by 400. So with a few calculations tweek the calendar by skipping 3 of 4 century leap years to average out our calendar year to 365.2425, which is pretty darn close to the solar year 365.24219.
Here’s the history:
The Romans originally had a 355-day calendar. To keep up with the seasons, an extra 22 or 23-day month was inserted every second year. For reasons unknown, this extra month was only observed now and then. By Julius Caesar’s time, the seasons no longer occurred at the same calendar periods as history had shown. To correct this, Caesar eliminated the extra month and added one or two extra days to the end of various months (his month included, which was Quintilis, later renamed Julius we know it as July). This extended the calendar to 365 days. Also intended was an extra calendar day every fourth year (following the 28th day of Februarius). However, after Caesar’s death in 44 B.C., the calendars were written with an extra day every 3 years instead of every 4 until corrected in 8 A.D. So again, the calendar drifted away from the seasons. By 1582, Pope Gregory XIII recognized that Easter would eventually become closer and closer to Christmas. The calendar was reformed so that a leap day would occur in any year that is divisible by 4 but not divisible by 100 except when the year is divisible by 400. Thus 1600 and 2000, although century marks, have a Leap Day.
The calendar we use today, known as the Gregorian calendar, makes our year 365.2425 days only off from our solar year by .00031, which amounts to only one day’s error after 4,000 years.
here is the story even more in depth
Februray 29th - Leap Day - 2000
If you're like most people, you shudder at the thought of one more Y2K
headache, millenium bug, computer glitch, or Spam-storing person camping out
in a makeshift fort waiting for the world to end. The world did not end and
it's not going to. But this thought was real-- just momentarily for some,
yet in others' minds for years: how to get around potential disasters
resulting from a few misplaced numbers?
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Which brings us to today, February 29, a day created just to get around
potential disasters. Leap Day, a day born long ago out of calculation
dilemmas similar to those we faced more recently. Despite thousands of
high-paid techies and millions of dollars in innovative software, we were
still left struggling in Y2K with a number crunch equal to the one faced by
team of abacus-toting scientists and mathematicians in 1582. How
far have we come? It took nearly 1600 years of fine-tuning our modern-day
calendar to avoid such disasters as snow falling in July and sunbathing in
November. The flaws encountered within the otherwise ingenious Roman Calendar
make for Leap Day's unique history.
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The original Roman 355 day calendar had an extra 22-day month every few years
to maintain the correct seasonal changes. By the time Julius Caesar took
reign, the seasons no longer occurred during the same months they once had.
Panicking, he remedied this in 44 B.C. by tossing the extra month and adding
the extra day to a few months instead. He threw in a month in honor of
himself (Julius-- July) and died a happy man having solved the calendar woes.
Not quite. Still creating seasonal confusion, the calendar was again changed,
first from an extra day every 3 years, to one every 4 years in 8 A.D. It was
then finally perfected with some complicated logic by Pope Gregory XIII in
1582 (who predicted Easter and Christmas would eventually fall on top of each
other without his divine intervention). He determined that Leap Day should
fall on any year divisible by 4 but not 100 (except when the year is
divisible by 400), setting up a calendar nearly identical to that of Mother
Nature. Thus, today our year is 365.2425 days, off from our solar year by
.00031, or one day's error over 4,000 years. Not bad. And without this
extra day, who knows of the chaos that might have ensued?
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If you're a "Leaper," you will celebrate today with passion close to the
fervor of this past New Year's Eve. Party till you drop; make up for the 3
years you spent watching friends and family hit milestone birthdays on days
that actually exist. Cherish the fact that you have beaten the 1,506 odds
against being born on Leap Day, into this secret society, a parallel universe
that flashes before our eyes every 4 years restoring order to all mankind.
Sigh some relief that you don't have to spend Birthday 2000 on February 28th
or March 1st, pretending again. If you're 40, convince yourself you're 10 and
reconnect with your inner child. Throw a party with Frog Legs, Hops, and
Grasshopper Pie on the menu, and serve Leap Year Cocktails. Join the
Worldwide Leap Year Birthday Club and attend the Worldwide Leap Year
Festival. And buy one of those annoying desktop zodiak calendars you've
always wanted, to read your real birthday horoscope!
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If you're a woman, wait no longer for that engagement ring-- today, Sadie
Hawkins day, is your day to propose marriage. This tradition originates in
Ireland in the 5th century, when St. Bridget convinced St. Patrick to allow
one day that a woman could propose. If the man refused, he was fined
(incidentally, St. Bridget proposed to St. Patrick that day; he said no).
1,600 years later, the fine has been ousted (who's idea was that?), but women
still have only this one day every 4 years set aside to profess their love
and commitment for the men in their lives. Again, just how far have we come?
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For most not fortunate enough to celebrate a birthday today, it may be simply
an extra day we have to trudge to work without getting paid. Even so, it's
one special day out of every 1,460 that somehow, in the grand scheme of
things, prevents seasons from colliding and keeps life interesting.