"අධික අවුරුද්ද" හි සංශෝධන අතර වෙනස්කම්

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1 පේළිය:
{{පරිවර්තනය නොනිමි|ඉංග්‍රීසි|Leap year}}
{{සැකිල්ල:පරිවර්ථනය කළ යුතු}}
'''අධික අවුරුද්ද''' යනු year containing one or more extra days (or, in the case of [[lunisolar calendar]]s, an extra month) in order to keep the [[calendar year]] synchronised with the [[astronomical year|astronomical]] or [[seasonal year]]. For example, in the [[Gregorian calendar]], February in a leap year has 29 days instead of the usual 28 so the year lasts 366 days instead of the usual 365. Because seasons and astronomical events do not repeat in a [[whole number]] of days, a calendar that had the same number of days in each year would, over time, drift with respect to the event it was supposed to track. By occasionally inserting (or ''[[intercalation|intercalating]]'') an additional day or month into the year, the drift can be corrected. A year that is ''not'' a leap year is called a ''[[common year]]''.
 
5 පේළිය:
[[ග්‍රෙගරි දින දසුන]], the current standard calendar in most of the world, most years whose division by 4 equals an [[integer]] are leap years. In each leap year, the month of February has 29 days instead of 28. Adding an extra day to the calendar every four years compensates for the fact that a period of 365 days is shorter than a [[solar year]] by almost 6 hours.
 
However, some exceptions to this rule are required since the duration of a solar year is slightly ''less'' than 365.25 days. 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.<ref name="rog">[http://www.nmm.ac.uk/server/show/conWebDoc.349 Royal Observatory, Greenwich: Leap years]</ref><ref name="usno"> [http://aa.usno.navy.mil/faq/docs/leap_years.php USNO (U.S. Naval Observatory): Leap Years]</ref> 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. The Gregorian calendar was designed to keep the [[vernal equinox]] on or close to March 21, so that the date of [[Easter]] (celebrated on the Sunday after the 14th day of the Moon—i.e. a [[full moon]]—that falls on or after March 21) remains correct with respect to the vernal equinox.<ref>E.G. Richards, ''Mapping time: The calendar and its history'', p. 240, ISBN 0-19-282065-7</ref> The vernal equinox year is about 365.242374 days long (and increasing).
 
The marginal difference of 0.000125 days between the Gregorian calendar average year and the actual year means that, in around 8,000 years, the calendar will be about one day behind where it is now. But in 8,000 years, the length of the vernal equinox year will have changed by an amount that cannot be accurately predicted (see below). Therefore, the current Gregorian calendar suffices for practical purposes, and the correction suggested by [[John Herschel]] of making 4000 a non-leap year will probably not be necessary.
 
{| width=640
|[[ගොනුව:Gregoriancalendarleap.png]]<br />''This graph shows the variation between the seasonal year and the calendar year due to unequally spaced 'leap days' rules. See [[Iranian calendar#Seasonal error|Iranian calendar]] to contrast with a calendar based on 8 leap days every 33 years.''
|}
 
==== Algorithm ====
 
<!-- do not add any other examples of algorithms -->
 
This algorithm determines leap years on the [[proleptic Gregorian calendar]], which includes leap years before the official inception in 1582.
 
[[Pseudocode]] to determine whether a year is a ''leap year'' or ''not'':
 
'''if''' year [[Modulo operation|modulo]] 400 is 0 '''then''' leap
'''else if''' year modulo 100 is 0 '''then''' no_leap
'''else if''' year modulo 4 is 0 '''then''' leap
'''else''' no_leap
 
A more direct algorithm (terms may be grouped either way):
'''function''' isLeapYear (year):
'''if''' ((year modulo 4 is 0) '''and''' (year modulo 100 is not 0)) '''or''' (year modulo 400 is 0)
'''then''' true
'''else''' false
 
=== Leap day ===
{{main|February 29}}
February 29 is a date that usually occurs every four years, and is called leap day. This day is added to the calendar in leap years as a corrective measure, because the earth does not orbit around the sun in precisely 365 days.
 
The Gregorian calendar is a modification of the [[Julian calendar]] first used by the Romans. The [[Roman calendar]] originated as a [[lunisolar calendar]] and named many of its days after the [[syzygy|syzygies]] of the moon: the new moon (''Kalendae'' or calends, hence "calendar") and the [[full moon]] (''Idus'' or ides). The ''Nonae'' or nones was not the first [[Lunar phase|quarter moon]] but was exactly one ''nundinae'' or Roman market week of nine days before the ides, inclusively counting the ides as the first of those nine days. In 1825, [[Christian Ludwig Ideler|Ideler]] believed that the lunisolar calendar was abandoned about 450 BC by the [[decemvirs]], who implemented the [[Roman calendar|Roman Republican calendar]], used until 46 BC. The days of these calendars were counted down (inclusively) to the next named day, so February 24 was ''ante diem sextum Kalendas Martii'' ("the sixth day before the calends of March") often abbreviated a. d. VI Kal. Mar. [[Ancient Rome|The Romans]] counted days inclusively in their calendars, so this was actually the fifth day before March 1 when counted in the modern exclusive manner (not including the starting day).<ref>Thomas Hewitt Key, [http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Calendarium.html Calendarium] (1875)</ref>
 
The Republican calendar's intercalary month was inserted on the first or second day after the [[Terminus (mythology)|Terminalia]] (a. d. VII Kal. Mar., February 23). The remaining days of Februarius were dropped. This intercalary month, named Intercalaris or [[Mercedonius]], contained 27 days. The religious festivals that were normally celebrated in the last five days of February were moved to the last five days of Intercalaris. Because only 22 or 23 days were effectively added, not a full lunation, the calends and ides of the Roman Republican calendar were no longer associated with the new moon and full moon.
 
The [[Julian calendar]], which was developed in 46 BC by [[Julius Caesar]], and became effective in 45 BC, distributed an extra ten days among the months of the Roman Republican calendar. Caesar also replaced the intercalary month by a single intercalary day, located where the intercalary month used to be. To create the intercalary day, the existing ''ante diem sextum Kalendas Martii'' (February 24) was doubled, producing ''ante diem bis sextum Kalendas Martii''. Hence, the year containing the doubled day was a bissextile (''bis sextum'', "twice sixth") year. For legal purposes, the two days of the ''bis sextum'' were considered to be a single day, with the second half being intercalated, but common practice by 238, when [[Censorinus]] wrote, was that the intercalary day was followed by the last five days of February, a. d. VI, V, IV, III and pridie Kal. Mar. (which would be those days numbered 24, 25, 26, 27, and 28 from the beginning of February in a common year), i.e. the intercalated day was the first half of the doubled day. All later writers, including [[Macrobius]] about 430, [[Bede]] in 725, and other medieval [[computus|computists]] (calculators of [[Easter]]), continued to state that the bissextum (bissextile day) occurred before the last five days of February.
 
Until 1970, the [[Roman Catholic Church]] always celebrated the feast of [[Saint Matthias]] on a. d. VI Kal. Mar., so if the days were numbered from the beginning of the month, it was named February 24 in common years, but the presence of the bissextum in a bissextile year immediately before a. d. VI Kal. Mar. shifted the latter day to February 25 in leap years, with the [[Vigil]] of St. Matthias shifting from February 23 to the leap day of February 24. Other feasts normally falling on February 25–28 in common years are also shifted to the following day in a leap year (although they would be on the same day according to the Roman notation). The practice is still observed by those who use the older calendars.
 
== Julian, Coptic and Ethiopian calendars ==
The [[Julian calendar]] adds an extra day to February in years evenly divisible by four.
 
The [[Coptic calendar]] and [[Ethiopian calendar]] also add an extra day to the end of the year once every four years before a Julian 29-day February.
 
This rule gives an average year length of 365.25 days. However, it is 11 minutes longer than a real year. This means that the vernal equinox moves a day earlier in the calendar every 131 years.
 
== Revised Julian calendar ==
The [[Revised Julian calendar]] adds an extra day to February in years divisible by four, except for years divisible by 100 that do not leave a remainder of 200 or 600 when divided by 900. This rule agrees with the rule for the Gregorian calendar until 2799. The first year that dates in the Revised Julian calendar will not agree with those in the Gregorian calendar will be 2800, because it will be a leap year in the Gregorian calendar but not in the Revised Julian calendar.
 
This rule gives an average year length of 365.242222… days. This is a very good approximation to the ''mean'' [[tropical year]], but because the ''vernal equinox'' year is slightly longer, the Revised Julian calendar does not do as good a job as the Gregorian calendar of keeping the vernal equinox on or close to March 21.
 
== සිංහල සහ චීන දින දසුන් ==
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The [[Hebrew calendar]] is also lunisolar with an embolismic month. This extra month is called ''Adar Alef'' ([[Adar 1|first Adar]]) and is added before ''[[Adar]]'', which then becomes ''Adar Bet'' ([[Adar 2|second Adar]]). According to the [[Metonic cycle]], this is done seven times every nineteen years (specifically, in years 3, 6, 8, 11, 14, 17, and 19).
 
In addition, the Hebrew calendar has postponement rules that postpone the start of the year by one or two days. These postponement rules reduce the number of different combinations of year length and starting [[days of the week]] from 28 to 14, and regulate the location of certain religious holidays in relation to the [[Shabbat|Sabbath]]. In particular, the first day of the Hebrew year can never be Sunday, Wednesday or Friday. This rule is known in Hebrew as "''lo adu rosh''", i.e. "Rosh [ha-Shanah, first day of the year] is not Sunday, Wednesday or Friday" (as the Hebrew word adu is written by three [[Hebrew alphabet|Hebrew letters]] signifying Sunday, Wednesday and Friday). Accordingly, the first day of [[Pesah]] (Passover) is never Monday, Wednesday or Friday. This rule is known in Hebrew as "''lo badu Pesah''", which has a double meaning — "Pesah is not a legend", but also "Pesah is not Monday, Wednesday or Friday" (as the Hebrew word ''badu'' is written by three Hebrew letters signifying Monday, Wednesday and Friday).
 
One reason for this rule is that [[Yom Kippur]], the holiest day in the Hebrew calendar, must never be adjacent to the weekly [[Shabbat|Sabbath]] (which is Saturday), i.e. it must never fall on Friday or Sunday, in order not to have two adjacent Sabbath days. However, Yom Kippur can be on Saturday.
 
Years consisting of 12 months have between 353 and 355 days. In a ''k'sidra'' ("in order") 354-day year, months have alternating 30 and 29 day lengths. In a ''chaser'' ("lacking") year, the month of [[Kislev]] is reduced to 29 days. In a ''malei'' ("filled") year, the month of [[Cheshvan]] is increased to 30 days. 13-month years follow the same pattern, with the addition of the 30-day Adar Alef, giving them between 383 and 385 days.
 
== ඉස්ලාම් දින දසුන ==
Line 77 ⟶ 22:
The months in the Islamic calender have 29 or 30 days.
 
== Calendars with leap years synchronized with Gregorian ==
The [[Indian National Calendar]] and the Revised [[Bangla Calendar]] of Bangladesh organise their leap years so that the leap day is always close to February 29 in the [[Gregorian calendar]]. This makes it easy to convert dates to or from Gregorian.
 
The [[Bahá'í calendar]] is structured such that the leap day always falls within [[Ayyám-i-Há]], a period of four or five days corresponding to Gregorian February 26 – March 1. Because of this, Baha'i dates consistently line up with exactly one Gregorian date.
 
The [[Thai solar calendar]] uses the [[Buddhist Era]] (BE), but has been synchronized with the Gregorian since [[AD]] 1941.
 
== හින්දු දින දසුන ==
Line 89 ⟶ 29:
The calendar followed in some parts of [[South India]] (mainly in Tamil Nadu) is [[solar]]. It has a leap year every four years.
 
== Iranian calendar ==
The [[Iranian calendar]] also has a single intercalated day once in every four years, but every 33 years or so the leap years will be five years apart instead of four years apart. The system used is more accurate and more complicated, and is based on the time of the March equinox as observed from [[Tehran]]. The 33-year period is not completely regular; every so often the 33-year cycle will be broken by a cycle of 29 or 37 years.
 
== Long term leap year rules ==
The accumulated difference between the Gregorian calendar and the vernal equinoctial year amounts to 1 day in about 8,000 years. This suggests that the calendar needs to be improved by another refinement to the leap year rule: perhaps by avoiding leap days in years evenly divisible by 8,000.
 
(The most common such proposal is to avoid leap years in years evenly divisible by 4,000.<ref>[http://www.google.com/search?q=%22gregorian+calendar%22+error+%22leap+year%22+4000 Google search for 4000-year rule]. </ref> This is based on the difference between the Gregorian calendar and the ''mean tropical year''. Others claim, erroneously, that the Gregorian calendar itself already contains a refinement of this kind.<ref>[http://www.straightdope.com/mailbag/mleapyr.html The Straight Dope with 4000-year rule]</ref>)
 
A system of 128-year-based leap years has been proposed,<ref>[http://stevegs.com/jd_calc/jd_calc.htm Julian Date Calculator]</ref> and it can be adopted directly without any modification to current leap year calculations until the year 2048 because no year between now and 2048 is divisible by 128. This rule gives a mean year of 365 + 1/4 − 1/128 = 365.2421875 days, which is 365 days, 5 hours, 48 minutes and 45 seconds, or one second short of the mean tropical year.
 
However, there is little point in planning a calendar so far ahead because over a timescale of tens of thousands of years the number of days in a year will change for a number of reasons, most notably:
# [[Precession of the equinoxes]] moves the position of the vernal equinox with respect to [[perihelion]] and so changes the length of the vernal equinoctial year.
# [[Tidal acceleration]] from the sun and moon slows the rotation of the earth, making the day longer.
 
In particular, the second component of change depends on such things as [[post-glacial rebound]] and [[sea level rise]] due to [[climate change]]. We can't predict these changes accurately enough to be able to make a calendar that will be accurate to a day in tens of thousands of years.
 
== Folk traditions ==
In the English speaking world, it is a [[tradition]] that women may propose marriage only on leap years. While it has been argued that the tradition was initiated by [[Saint Patrick]] or [[Brigid of Kildare]] in 5th century [[Ireland]], it is dubious as the tradition has not been attested before the 19th century.<ref>[http://www.snopes.com/oldwives/february29.asp The Privilege of Ladies by Barbara Mikkelson]</ref> Supposedly, a 1288 law by Queen [[Margaret, Maid of Norway|Margaret of Scotland]] (then age five and living in Norway), required that fines be levied if a marriage proposal was refused by the man; compensation ranged from a kiss to £1 to a silk gown, in order to soften the blow.<ref>Virtually no laws of Margaret survive. Indeed, none concerning her subjects are recorded in the twelve volume ''Acts of the Parliaments of Scotland'' (1814–75) covering the period 1124–1707 (two laws concerning young Margaret herself are recorded on pages 424 & 441–2 of volume I).</ref> Because men felt that put them at too great a risk, the tradition was in some places tightened to restricting female proposals to the modern leap day, February 29, or to the medieval leap day, February 24. According to Felten: "A play from the turn of the 17th century, 'The Maydes Metamorphosis,' has it that 'this is leape year/women wear breeches.' A few hundred years later, breeches wouldn't do at all: Women looking to take advantage of their opportunity to pitch woo were expected to wear a scarlet petticoat -- fair warning, if you will."<ref>[http://online.wsj.com/article/SB120371485815386581.html?mod=djemITP The Bissextile Beverage - WSJ.com<!-- Bot generated title -->]</ref>
 
In [[Denmark]], the tradition is that women may propose on leap day February 24 and that refusal must be compensated with 12 pairs of gloves.
 
In [[Greece]], it is believed that getting married in a leap year is bad [[luck]] for the couple {{Fact|date=February 2008}}. Thus, mainly in the middle of the past century, couples avoided setting a marriage date in a leap year.
<center><gallery>
Image:PostcardLeapYearBeCarefulClara1908.jpg|1908 postcard
Image:PostcardLeapYearMaidensAre1908.jpg|1908 postcard
File:PostcardTheMaidensVowIn1908.jpg
</gallery></center>
 
== Birthdays ==
 
A person born on February 29 may be called a "''leapling''" or a "''leaper''" <ref> {{Citation
| last = Hall
| first = Christina
| title = Leap year babies hop through hoops of joy, pain of novelty birthday
| newspaper = Detroit Free Press
| date = 2008-02-29
| url = http://www.freep.com/apps/pbcs.dll/article?AID=/20080229/NEWS05/802290352
| accessdate = 2008-02-29 }}
</ref>. In common years they usually celebrate their [[birthday]]s on February 28 or March 1.
 
For legal purposes, their legal birthdays depend on how different laws count time intervals. In [[Taiwan]], for example, the legal birthday of a leapling is February 28 in common years, so a Taiwanese leapling born on February 29, 1980 would have legally reached 18 years old on February 28, 1998.
 
{{quote|If a period fixed by weeks, months, and years does not commence from the beginning of a week, month, or year, it ends with the ending of the day which proceeds the day of the last week, month, or year which corresponds to that on which it began to commence.  But if there is no corresponding day in the last month, the period ends with the ending of the last day of the last month.<ref>Article 121 of the [[wikisource:Civil Code Part I General Principles|Civil Code Part I General Principles]] of the [[Republic of China]] in effect in Taiwan</ref>}}
 
In some situations, March 1 is used as the birthday in a non-leap year since it then is the day just after February 28.
 
Strictly speaking a leapling will have fewer birthdays than their age in years. That paradox is sometimes found in children's literature where a person's claim to be only a quarter of their actual age turns out to be based on counting their leap-year birthdays. The same birthday paradox in [[Gilbert and Sullivan]]'s 1879 [[comic opera]] ''[[The Pirates of Penzance]]'' comes as a shock to Frederic the pirate apprentice who finds that he is bound to serve the pirates until his 21st birthday instead of his 21st year.
 
According to [[DC Comics]] editor [[Julius Schwartz]], the birth date of [[Superman]] is February 29. This was chosen both as a way to keep the character young as well as account for the differences between Earth years and Kryptonian years.
 
== See also ==
* [[Century leap year]]
* [[Leap week calendar]]
* [[Leap second]]
* [[Zeller's congruence]]
 
== References ==
"https://si.wikipedia.org/wiki/අධික_අවුරුද්ද" වෙතින් සම්ප්‍රවේශනය කෙරිණි