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Why Do We Need Leap Days?
Life Little Mysteries ^ | 3/2/2012 | Alexey Repka

Posted on 03/03/2012 1:22:50 AM PST by U-238

Most years, the calendar hops straight from Feb. 28 to Mar. 1. But in almost all years whose numerical value is divisible by four, such as 2012, an extra "leap day" gets tacked on the end of the second month. Cue, today's date: Feb. 29.

The extra day must be added to every fourth calendar year in order to keep our Gregorian calendar synchronized with actual astronomical measures of the passage of time. According to the National Institute of Standards and Technology (NIST), the length of Earth's year — as in the time it takes for the planet to complete one revolution around the sun — is not a clean 365 days, but rather 365.2422. Adding an extra day to one-fourth of calendar years compensates for the buildup of partial days.

However, because the astronomical year isn't exactly 365.25 days long, but a hair shorter, the normal leap year schedule is a slight over-compensation. To scale back the full-day leaps and keep the calendar right on track, some century years (years with double zeroes at the end) are not leap years. The rule dictates that only century years which are divisible by 400, such as the year 2000, contain leap days. The numbers 1900, 1800 and 1700 aren't divisible by 400, and so those years were not leap years.

Altogether, the 400-year leap year cycle ensures that Earth is as close as possible to the same point in its orbit in consecutive calendar years. Any further errors that accumulate are corrected when needed through the addition of a leap second onto the last minute of either June or December. During leap seconds, the Coordinated Universal Time follows the sequence 23h 59m 59s - 23h 59m 60s - 00h 00m 00s.

(Excerpt) Read more at lifeslittlemysteries.com ...


TOPICS: Chit/Chat; Science
KEYWORDS: nist; science; trivia
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1 posted on 03/03/2012 1:22:54 AM PST by U-238
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To: U-238

Because if we didn’t there would be no Leap Nights?


2 posted on 03/03/2012 1:25:00 AM PST by Kickass Conservative (New Tagline under construction, please watch your step.)
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To: U-238

Say that again.


3 posted on 03/03/2012 1:26:21 AM PST by beaversmom
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To: U-238

This is an entertaining way to explain it.

http://m.youtube.com/watch?gl=CA&hl=en&client=mv-google&v=56zlm9qhVGc


4 posted on 03/03/2012 1:32:27 AM PST by Jonty30 (What Islam and secularism have in common is that they are both death cults.)
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To: Kickass Conservative

And without those leap nights, many married men would be celibate.

Woo hoo!


5 posted on 03/03/2012 1:34:36 AM PST by Jonty30 (What Islam and secularism have in common is that they are both death cults.)
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The motivation of the Catholic Church to adjusting the calendar was the celebration of Easter. The Council of Trent approved the plan to correct the errors in the calendar.First, it was necessary to approximate the correct length of a solar year.The second stage was to devise a model based on the approximation which would provide an accurate yet simple, rule-based calendar


6 posted on 03/03/2012 1:35:53 AM PST by U-238
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To: U-238

Before the Gregorian calendar, most countries relied on the Julian calendar, which was introduced by Julius Caesar in 45 BC. It was in common use until the 1500s. The Julian calendar creates an error of 1 day every 128 years.
The Gregorian calendar was proposed by Aloysius Lilius, a physician from Naples, and adopted by Pope Gregory XIII in accordance with the instructions from the Council of Trent (1545-1563) to correct for errors in the older Julian calendar. It was decreed by Pope Gregory XIII in a papal bull on February 24 1582. This bull was named “Inter Gravissimas” after its first two words.


7 posted on 03/03/2012 1:59:45 AM PST by U-238
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To: U-238

We need leap year because there is no connection whatsoever between the rotation of the earth and it’s orbit around the sun. Remember that the next time someone starts feeding you the Cosmic Watchmaker line.


8 posted on 03/03/2012 2:01:22 AM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: muir_redwoods

William Paley was one of the first people for the Cosmic Watchmaker arguement


9 posted on 03/03/2012 2:05:45 AM PST by U-238
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To: muir_redwoods

Although Cicero, Voltaire and René Descartes, for example, used timepieces in arguments regarding purpose


10 posted on 03/03/2012 2:07:35 AM PST by U-238
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To: muir_redwoods

Well, that’s a non sequiter if ever I heard one.


11 posted on 03/03/2012 2:07:52 AM PST by Boogieman
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To: Boogieman

I can explain it for you but I can’t understand it for you. The gears in a watch sync up pretty closely. They all relate to each other in the manner in which they turn. There’s no need for a “leap gear” in a watch. See?


12 posted on 03/03/2012 2:16:50 AM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: U-238

Because fireworks look like crap in a blizzard?


13 posted on 03/03/2012 2:37:28 AM PST by BigCinBigD
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To: BigCinBigD

People born on Leap Day get squat for birthday presents three years out of four. They should be allowed to live four times as long. Pancake house is full on Leap Day for some reason. I went there Wednesday and the lines were out the door. Yet on Thursday, I got right in.


14 posted on 03/03/2012 2:53:14 AM PST by SamAdams76 (I am 71 days away from outliving Phil Hartman)
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To: U-238

So I can have a birthday, newbie !


15 posted on 03/03/2012 3:13:05 AM PST by knarf (I say things that are true ... I have no proof ... but they're true)
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To: U-238
"The extra day must be added to every fourth calendar year...."

Yes, we know THAT, but why February and not, say June 31st or July 32nd?
Those are months we wouldn't mind being longer - living in New England, I would be Ok with a shorter February, maybe 21 days....

16 posted on 03/03/2012 3:21:58 AM PST by Psalm 73 ("Gentlemen, you can't fight in here - this is the War Room".)
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To: muir_redwoods

And how did you deduce that there exists no connection between the two?


17 posted on 03/03/2012 4:00:37 AM PST by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: U-238

I just want to know how I can add that six hours into my sleep time?


18 posted on 03/03/2012 4:14:45 AM PST by raybbr (People who still support Obama are either a Marxist or a moron.)
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To: Psalm 73

That’s funny. February was probably picked because it is the shortest month.

In the Chinese calendar leap months, “embolismic” months, almost always occur in the summer. Oriential wisdom, or the incidental consequence of Kepler’s second law? I pick the latter.

Most people are not aware that the Gregorian Solar Calendar has a sidekick lunar calendar, which is even more accurate than the Gregorian. The ecclesiastic age of the moon does not change on February 29, so that in both common years and leap years, the age of the moon on January 1 is the same as the age on March 1. This simplifies the computation of the date of Easter. The length of an ecclestiastic lunation alternates between 29 and 30 days, (with centuries scale corrections) so that March 1st is exactly 59 days after January 1st, if we do not count February 29 and therefore has the same lunar age.

In the Gregorian calendar, short months always follow long months, except for August (see, they were thinking about you), so that the lunar phase is retarded by about one day on the same day month to month except in September, where it slips about two days and in March, where it exactly follows January.


19 posted on 03/03/2012 4:58:28 AM PST by Lonesome in Massachussets (Ceterum autem censeo, Obama delenda est.)
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To: Psalm 73

Say, are you related to that lady who was against daylight saving time because the extra hour of sunlight would burn her grass?


20 posted on 03/03/2012 4:59:48 AM PST by mc5cents
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To: U-238
This also explains why George Washington has two birthdays. On the day he was born, the calendar said it was February 11. However, the accrued errors from the Julian calendar made the day to be February 22 when England switched to the Gregorian calendar. Now the geniuses in Washington DC declare it to be the third Monday in February, making it to be in error most of the time, and don't even call it George Washington's birthday any more.
21 posted on 03/03/2012 5:08:29 AM PST by norwaypinesavage (Galileo: In science, the authority of a thousand is not worth the humble reasoning of one individual)
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To: norwaypinesavage

I remember reading in some old history books the notation (O/S) meaning “Old Style” for a given date in colonial history. I don’t think historians bother with it any more.


22 posted on 03/03/2012 5:18:56 AM PST by Oratam
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To: U-238

This girl doesn’t understand leap years.
(warning: bad language)
http://www.youtube.com/watch?feature=player_embedded&v=pK-frJtGrt4


23 posted on 03/03/2012 5:21:49 AM PST by Jack Hydrazine (It's the end of the world as we know it and I feel fine!)
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To: Psalm 73
Yes, we know THAT, but why February and not, say June 31st or July 32nd?

The Romans started their civil year on March 1, not January 1. That's why September, October, November, and December have names deriving from the Latin for seven, eight, nine, and ten -- they were originally the seventh, eighth, ninth, and tenth months.

February was the short month tacked on at the end of the year because there weren't 30 or 31 days left to fill out a full month.

24 posted on 03/03/2012 5:38:16 AM PST by Campion ("It is in the religion of ignorance that tyranny begins." -- Franklin)
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To: U-238

So women like Sandra Fluke can get a date.


25 posted on 03/03/2012 6:00:20 AM PST by ALPAPilot
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To: U-238

We need Leap Year now so that we have to put up with Black History month for an extra day every 4 years.


26 posted on 03/03/2012 6:19:49 AM PST by crosshairs (Maranatha!)
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To: count-your-change

Because the orbital period of the earth around the sun is about 365.2564 days and the rotational period of the earth is, by definition(with some variation) 24 hours. Point out the connection please.

Some watch


27 posted on 03/03/2012 6:31:41 AM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: Psalm 73
<"The extra day must be added to every fourth calendar year...."

Try this answer: If we did not do the correction, the calendar would run backward after 365 years. ROFLMAO

28 posted on 03/03/2012 6:46:12 AM PST by Rapscallion (The best way to enforce "fairness" is tyranny. Begone Obama.)
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To: BigCinBigD

LOL!


29 posted on 03/03/2012 6:55:01 AM PST by 6SJ7 (Meh.)
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To: muir_redwoods
That's exactly right. There isn't supposed to be any direct relationship between the rotation of the earth and its revolution around the sun. As humans we have simply acclimated ourselves to a self-made world in which "time" is expected to be measured in defined increments even if they make no sense in the physical world.

A "day," for example, is a measure of real time -- as is a "year." But the notion that a "year" begins and ends at the exact start/finish of a "day" is purely a human construct.

A "month" is loosely based on lunar cycles, but there is nothing that ties months directly to days and years, either.

30 posted on 03/03/2012 7:05:34 AM PST by Alberta's Child ("If you touch my junk, I'm gonna have you arrested.")
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To: U-238
Solar time is a reckoning of the passage of time based on the Sun's position in the sky. The fundamental unit of solar time is the day. Two types of solar time are apparent solar time (sundial time) and mean solar time (clock time).

A solar year (also known as a tropical year), for general purposes, is the length of time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth.

Sidereal time, the amount of time required for the earth to make a complete rotation around its axis is 23 hours, 56 minutes and four seconds (23:56:04) instead of 24 hours (24:00:00)

A leap year (or intercalary or bissextile year) is a year containing one additional day (or, in the case of lunisolar calendars, a month) in order to keep the calendar year synchronized with the astronomical or seasonal year.

31 posted on 03/03/2012 7:08:42 AM PST by E. Pluribus Unum (Government is the religion of the sociopaths.)
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To: U-238

When I was a kid, I read somewhere that the reason a year is such a screwy number is explained biblically. In the Bible there are passages, but I can only remember one, where an Israeli general prayed to God that night wouldn’t occur during a batlle, because then the enemy would be able to flee. God obliged and kept the sun from setting until the battle was done. TDon’t know if that’s why we have an extra day, but it works for me.


32 posted on 03/03/2012 7:13:48 AM PST by chae (I was anti-Obama before it was cool)
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To: muir_redwoods

Well, that’s a different argument than the classical “Cosmic Watchmaker” argument. Still, I think it’s flawed. You are assuming the “watchmaker” intended the gears to match up in the way that you would expect or prefer. I can see no solid logical basis for making that assumption.


33 posted on 03/03/2012 7:35:53 AM PST by Boogieman
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To: Alberta's Child

Exactly. Expecting them all to line up is just pure human conceit.

Now, if you are a Christian, you could try to make an argument from Genesis, about God setting the lights in the heaven for us to measure the times and seasons, and then wonder why they are not aligned more perfectly in order to facilitate that. If you want to make that argument, though, then you already have to accept the proposition of the Biblical God at work, and then you’d also have to accept the proposition that God’s will is not always comprehensible to us, so your argument would be self-defeating.


34 posted on 03/03/2012 7:39:36 AM PST by Boogieman
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To: Boogieman

If the analogy is to watch where the gears match up precisely, my expectation that the rotation and the orbit match precisely us a reasonable, even necessary one. I cannot explain the obvious any further.


35 posted on 03/03/2012 7:40:34 AM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: chae

Some Creationists argue that perhaps, as a consequence of the flood catasphrophe, or maybe when the “world was divided” at the time of the Tower of Babel, the Earth could have lost some of its mass. That would have affected the rate of spin and the velocity of the Earth and changed the length of days and years.

Not something you can prove through Scripture, but it would be an interesting correlary to how man became flawed, with shorter and shorter lifespans after the fall, if the Earth itself became flawed too.


36 posted on 03/03/2012 7:43:29 AM PST by Boogieman
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To: muir_redwoods

Well the Watchmaker analogy, as it is posited, has nothing to do with the gears of a watch related to the connection between days and years on Earth.

As for your version of it, it’s just a conceit. You are looking for the gears to sync up in the way that you would expect, but there is no objective reason why that should be the case. Every planet has different day lengths and year lengths, some radically different than ours. The whole system keeps spinning along, but you want there to be some perfect correlation between days and years in nice round numbers, in a manner that you define, and when you don’t find that, you’re basically saying that you have won an argument. In reality, all you’ve done is set up a straw man and take that straw man down. It’s a flawed argument to begin with, so it means nothing at all if you are able to negate it.


37 posted on 03/03/2012 7:50:31 AM PST by Boogieman
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To: Boogieman

This is getting tiresome. There is no connection between the rotation of the earth and its orbit. That was my point. The two events are unrelated and any analysis of the two phenomena points to randomness rather than design. Period


38 posted on 03/03/2012 8:49:42 AM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: muir_redwoods

The connection would be the mass. But it seems the real objection you have is the comparison to a watch.


39 posted on 03/03/2012 9:02:55 AM PST by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: muir_redwoods

“The two events are unrelated and any analysis of the two phenomena points to randomness rather than design. Period”

Now you’re resorting to circular argument. You can only say it points to randomness if you accept as a given that there should be a correlation between them if there is a designer. You have offered no argument as to why we should expect there would be, you just assume that, apparently because it suits your argument.

You argument, condensed, boils down to: “If there was a designer, the days and years should be in sync. The days and years aren’t in sync, therefore, there is no designer.” That is textbook circular reasoning, I hope you can see that.


40 posted on 03/03/2012 9:07:43 AM PST by Boogieman
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To: count-your-change; muir_redwoods

Yes, there is a connection of course, just not the connection he is looking for.

1 year = 365.242199~ days

That is a correlation, just not one that is expressed in nice round numbers. It does not follow that this is, therefore, any evidence of randomness, unless one doesn’t understand the everpresent nature of irrational numbers in the universe.

1 Circumference = 3.1415927~ diameters

That is not a nice round number correlation either, yet who would argue that the existence of circles is evidence of randomness vs design?


41 posted on 03/03/2012 9:14:44 AM PST by Boogieman
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To: Boogieman

I’m on the side of design.


42 posted on 03/03/2012 9:29:09 AM PST by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: count-your-change

Yes, I figured as much, just thought I would ping you since I was responding to elaborate on the point you were making to him, that there is, in fact, a clear correlation.


43 posted on 03/03/2012 9:38:49 AM PST by Boogieman
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To: Boogieman
Well, feel free to jump in as you wish. I appreciate the opportunity to hear other’s thoughts.
44 posted on 03/03/2012 9:47:31 AM PST by count-your-change (You don't have to be brilliant, not being stupid is enough.)
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To: muir_redwoods
muir_redwoods said: There’s no need for a “leap gear” in a watch.

There's a need for one in my inexpensive Timex. It indicated March 1'st all day on February 29th.

45 posted on 03/03/2012 11:27:09 AM PST by William Tell
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To: U-238
I suggest that we adopt the Jewish lunar calendar. That way you do away with a "leap day." Instead they have a "leap month." A second month of "Adar." Much easier.

Mark

46 posted on 03/03/2012 12:21:51 PM PST by MarkL (Do I really look like a guy with a plan?)
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To: knarf

At this point, I am far from a newbie, right?


47 posted on 03/03/2012 3:33:24 PM PST by U-238
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To: count-your-change

Which is where I started and the only point I was making


48 posted on 03/03/2012 3:35:46 PM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: Boogieman

No, the obvious point I’ve been making is that there is no connection between rotational and orbital periods for the earth. There is either some hidden amusement value in adopting a stance of volitional ignorance on the part of people reading my statements on this matter if there is a depressing degree of genuine ignorance for those people.


49 posted on 03/03/2012 4:37:02 PM PST by muir_redwoods (No wonder this administration favors abortion; everything they have done is an abortion)
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To: muir_redwoods
No, the obvious point I’ve been making is that there is no connection between rotational and orbital periods for the earth. There is either some hidden amusement value in adopting a stance of volitional ignorance on the part of people reading my statements on this matter if there is a depressing degree of genuine ignorance for those people.

I’m not sure what you’re point is here. It’s the Earth’s tilt that accounts for the seasons and to some extent, its elliptical orbit around the Sun.

The Earth’s rotation accounts for the time between Sunrise and Sunset but that’s not exactly 24 hours. The Earth orbits the Sun but not in exactly 365 days.

If our current 24 hour day clock and 365 day calendar didn’t account for this with a leap day every four years, eventually Spring would fall on our calendar sometime in September.

50 posted on 03/03/2012 4:54:04 PM PST by MD Expat in PA
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