Leap year

A leap year (also known as an intercalary year or bissextile year) is a calendar year containing one additional day (or, in the case of lunisolar calendars, a month) added to keep the calendar year synchronized with the astronomical or seasonal year.[1] Because seasons and astronomical events do not repeat in a whole number of days, calendars that have the same number of days in each year drift over time with respect to the event that the year is supposed to track. By inserting (also called 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.

For example, in the Gregorian calendar, each leap year has 366 days instead of 365, by extending February to 29 days rather than the common 28. These extra days occur in years which are multiples of four (with the exception of centennial years not divisible by 400). Similarly, in the lunisolar Hebrew calendar, Adar Aleph, a 13th lunar month, is added seven times every 19 years to the twelve lunar months in its common years to keep its calendar year from drifting through the seasons. In the Bahá'í Calendar, a leap day is added when needed to ensure that the following year begins on the vernal equinox.

The name "leap year" probably comes from the fact that while a fixed date in the Gregorian calendar normally advances one day of the week from one year to the next, the day of the week in the 12 months following the leap day (from March 1 through February 28 of the following year) will advance two days due to the extra day (thus "leaping over" one of the days in the week).[2][3] For example, Christmas Day (December 25) fell on a Sunday in 2016, and Monday in 2017, then it fell on Tuesday in 2018, and will fall on Wednesday in 2019 but then "leaps" over Thursday to fall on a Friday in 2020.

The length of a day is also occasionally changed by the insertion of leap seconds into Coordinated Universal Time (UTC), owing to the variability of Earth's rotational period. Unlike leap days, leap seconds are not introduced on a regular schedule, since the variability in the length of the day is not entirely predictable.

Gregorian calendar

Leap Centuries
An image showing which century years are leap years in the Gregorian calendar.

In the Gregorian calendar, the standard calendar in most of the world, most years that are multiples of 4 are leap years. In each leap year, the month of February has 29 days instead of 28. Adding one extra day in the calendar every four years compensates for the fact that a period of 365 days is shorter than a tropical year by almost 6 hours.[4] Some exceptions to this basic rule are required since the duration of a tropical year is slightly less than 365.25 days. The Gregorian reform modified the Julian calendar's scheme of leap years as follows:

Every year that is exactly divisible by four is a leap year, except for years that are exactly divisible by 100, but these centurial years are leap years if they are exactly divisible by 400. For example, the years 1700, 1800, and 1900 are not leap years, but the year 2000 is.[5]

Over a period of four centuries, the accumulated error of adding a leap day every four years amounts to about three extra days. The Gregorian calendar therefore drops three leap days every 400 years, which is the length of its leap cycle. This is done by dropping February 29 in the three century years (multiples of 100) that cannot be exactly divided by 400.[6][7] The years 1600, 2000 and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200 and 2300 are common years. By this rule, the average number of days per year is 365 + ​14 − ​1100 + ​1400 = 365.2425.[8] The rule can be applied to years before the Gregorian reform (the proleptic Gregorian calendar), if astronomical year numbering is used.[9]

Gregoriancalendarleap solstice

This graph shows the variations in date and time of the June Solstice due to unequally spaced "leap day" rules. Contrast this with the Iranian Solar Hijri calendar, which generally has 8 leap year days every 33 years.

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 ecclesiastical full moon that falls on or after March 21) remains close to the vernal equinox.[10][8] The "Accuracy" section of the "Gregorian calendar" article discusses how well the Gregorian calendar achieves this design goal, and how well it approximates the tropical year.

Algorithm

The following pseudocode determines whether a year is a leap year or a common year in the Gregorian calendar (and in the proleptic Gregorian calendar before 1582). The year variable being tested is the integer representing the number of the year in the Gregorian calendar.

if (year is not divisible by 4) then (it is a common year)
else if (year is not divisible by 100) then (it is a leap year)
else if (year is not divisible by 400) then (it is a common year)
else (it is a leap year)

The algorithm applies to proleptic Gregorian calendar years before 1, but only if the year is expressed with astronomical year numbering. It is not valid for the BC or BCE notation. The algorithm is not necessarily valid for years in the Julian calendar, such as years before 1752 in the British Empire. The year 1700 was a leap year in the Julian calendar, but not in the Gregorian calendar.

Leap day

Calendar-leapyeardate
A Swedish pocket calendar from 2008 showing February 29
Japanese Calendar with Verses by Osman Edwards 1900 February
February 1900 calendar showing that 1900 was not a leap year

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 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 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 quarter moon but was exactly one nundina or Roman market week of nine days before the ides, inclusively counting the ides as the first of those nine days. This is what we would call a period of eight days. In 1825, Ideler believed that the lunisolar calendar was abandoned about 450 BC by the decemvirs, who implemented the 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 Martias ("the sixth day before the calends of March") often abbreviated a. d. VI Kal. Mart. 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).[11]

The Republican calendar's intercalary month was inserted on the first or second day after the 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 Martias (February 24) was doubled, producing ante diem bis sextum Kalendas Martias. 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 in common practice by 238, when Censorinus wrote, the intercalary day was followed by the last five days of February, a. d. VI, V, IV, III and pridie Kal. Mart. (the days numbered 24, 25, 26, 27, and 28 from the beginning of February in a common year), so that the intercalated day was the first half of the doubled day. Thus the intercalated day was effectively inserted between the 23rd and 24th days of February. All later writers, including Macrobius about 430, Bede in 725, and other medieval computists (calculators of Easter), continued to state that the bissextum (bissextile day) occurred before the last five days of February.

MissaleLeapYear
In the older Roman Missal, feast days falling on or after February 24 are celebrated one day later in leap year.

Until 1970, the Roman Catholic Church always celebrated the feast of Saint Matthias on a. d. VI Kal. Mart., 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. Mart. 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. This shift did not take place in pre-Reformation Norway and Iceland; Pope Alexander III ruled that either practice was lawful (Liber Extra, 5. 40. 14. 1). 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.

Synchronized calendars (Bengali, Indian and Thai)

The Revised Bengali Calendar of Bangladesh and the Indian National Calendar organise their leap years so that the every leap day is close to a February 29 in the Gregorian calendar and vice versa. This makes it easy to convert dates to or from Gregorian.

The Thai solar calendar uses the Buddhist Era (BE), but has been synchronized with the Gregorian since AD 1941.

Julian, Coptic and Ethiopian calendars

From AD 8 the Julian calendar received an extra day added to February in years that are multiples of 4.

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 tropical year. This means that the vernal equinox moves a day earlier in the calendar about every 131 years.

Revised Julian calendar

The Revised Julian calendar adds an extra day to February in years that are multiples of four, except for years that are multiples of 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 for the time being does not do as good a job as the Gregorian calendar at keeping the vernal equinox on or close to March 21.

Chinese calendar

The Chinese calendar is lunisolar, so a leap year has an extra month, often called an embolismic month after the Greek word for it. In the Chinese calendar the leap month is added according to a rule which ensures that month 11 is always the month that contains the northern winter solstice. The intercalary month takes the same number as the preceding month; for example, if it follows the second month (二月) then it is simply called "leap second month" i.e. simplified Chinese: 闰二月; traditional Chinese: 閏二月; pinyin: rùn'èryuè.

Hebrew calendar

The Hebrew calendar is lunisolar with an embolismic month. This extra month is called Adar Alef (first Adar) and is added before Adar, which then becomes Adar Bet (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). This is to ensure that Passover (Pesah) is always in the spring as required by the Torah (Pentateuch) in many verses[12] relating to Passover.

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 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" (לא אד"ו ראש), 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 letters signifying Sunday, Wednesday and Friday). Accordingly, the first day of Passover is never Monday, Wednesday or Friday. This rule is known in Hebrew as "lo badu Pesah" (לא בד"ו פסח), which has a double meaning — "Passover is not a legend", but also "Passover 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 and the tenth day of the Hebrew year, now must never be adjacent to the weekly 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 still be on Saturday. These rules for the Feasts do not apply to the years from the Creation to the deliverance of the Hebrews from Egypt under Moses. It was at that time (cf. Exodus 13) that the God of Abraham, Isaac and Jacob gave the Hebrews their "Law" including the days to be kept holy and the feast days and Sabbaths.

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 Marcheshvan 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.

Islamic calendar

The observed and calculated versions of the Islamic calendar do not have regular leap days, even though both have lunar months containing 29 or 30 days, generally in alternating order. However, the tabular Islamic calendar used by Islamic astronomers during the Middle Ages and still used by some Muslims does have a regular leap day added to the last month of the lunar year in 11 years of a 30-year cycle.[13] This additional day is found at the end of the last month, Dhu 'l-Hijja, which is also the month of the Hajj.[14]

The Hijri-Shamsi calendar, also adopted by the Ahmadiyya Muslim Community, is based on solar calculations and is similar to the Gregorian calendar in its structure with the exception that the first year starts with Hijra.[15]

Hindu calendar

In the Hindu calendar, which is a lunisolar calendar, the embolismic month is called adhika maas (extra month). It is the month in which the sun is in the same sign of the stellar zodiac on two consecutive dark moons. Adhika maas occurs once every 33 to 34 months, compensating for the approximately eleven fewer days per year in twelve lunar months than the solar calendar. Thus, Hindu festivals tend to occur within a given span of the Gregorian calendar. For example: the No Moon during Diwali festival occurs between mid-October and mid-November. Buddhist calendars in several related forms (each a simplified version of the Hindu calendar) are used on mainland Southeast Asia in the countries of Cambodia, Laos, Thailand, Myanmar (formerly Burma) and Sri Lanka.

The Hindu Calendar also known as Vikram Samvat is used in Nepal as the national calendar. All the official work is done based on this calendar.

The calendar followed in some parts of South India (mainly in Tamil Nadu) is solar. It has a leap year every four years.

Bahá'í calendar

The Bahá'í calendar is a solar calendar composed of 19 months of 19 days each (361 days). Years begin at Naw-Rúz, on the vernal equinox, on or about March 21. A period of "Intercalary Days", called Ayyam-i-Ha, are inserted before the 19th month. This period normally has 4 days, but an extra day is added when needed to ensure that the following year starts on the vernal equinox. This is calculated and known years in advance.

Solar Hijri calendar

The Iranian calendar is an observational calendar that starts on the spring equinox and adds a single intercalated day to the last month (Esfand) once every four or five years; the first leap year occurs as the fifth year of the typical 33-year cycle and the remaining leap years occur every four years through the remainder of the 33-year cycle. 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 years. [16]

Jalaali Leap Year

Jalaali Leap Year

Folk traditions

Bob Satterfield cartoon about leap year traditions
A spinster eagerly awaits the upcoming leap day, in this 1903 cartoon by Bob Satterfield.

In Ireland and Britain, it is a tradition that women may propose marriage only in leap years. While it has been claimed that the tradition was initiated by Saint Patrick or Brigid of Kildare in 5th century Ireland, this is dubious, as the tradition has not been attested before the 19th century.[17] Supposedly, a 1288 law by Queen 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 was deemed to be a pair of leather gloves, a single rose, £1 and a kiss.[18] In some places the tradition was tightened to restricting female proposals to the modern leap day, February 29, or to the medieval (bissextile) 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."[19]

In Finland, the tradition is that if a man refuses a woman's proposal on leap day, he should buy her the fabrics for a skirt.[20]

In France, since 1980, a satirical newspaper entitled La Bougie du Sapeur is published only on leap year, on February 29.

In Greece, marriage in a leap year is considered unlucky.[21] One in five engaged couples in Greece will plan to avoid getting married in a leap year.[22]

In February 1988 the town of Anthony in Texas, declared itself "leap year capital of the world", and an international leapling birthday club was started.[23]

PostcardLeapYearBeCarefulClara1908

Woman capturing man with butterfly-net.

PostcardLeapYearMaidensAre1908

Women anxiously awaiting January 1

PostcardTheMaidensVowIn1908

Histrionically preparing

Birthdays

A person born on February 29 may be called a "leapling" or a "leaper".[24] In common years, they usually celebrate their birthdays on February 28. In some situations, March 1 is used as the birthday in a non-leap year, since it is the day following February 28.

Technically, a leapling will have fewer birthday anniversaries than their age in years. This phenomenon is exploited when a person claims to be only a quarter of their actual age, by counting their leap-year birthday anniversaries only: for example, in Gilbert and Sullivan's 1879 comic opera The Pirates of Penzance, Frederic the pirate apprentice discovers that he is bound to serve the pirates until his 21st birthday (that is, when he turns 88 years old, since 1900 was not a leap year) rather than until his 21st year.

For legal purposes, legal birthdays depend on how local laws count time intervals.

Republic of China

The Civil Code of the Republic of China since October 10, 1929,[25] implies that the legal birthday of a leapling is February 28 in common years:

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 precedes 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.[26]

Hong Kong

Since 1990 non-retroactively, Hong Kong considers the legal birthday of a leapling March 1 in common years:[27]

  1. The time at which a person attains a particular age expressed in years shall be the commencement of the anniversary corresponding to the date of [their] birth.
  2. Where a person has been born on February 29 in a leap year, the relevant anniversary in any year other than a leap year shall be taken to be March 1.
  3. This section shall apply only where the relevant anniversary falls on a date after the date of commencement of this Ordinance.

See also

References

  1. ^ Meeus, Jean (1998), Astronomical Algorithims, Willmann-Bell, p. 62
  2. ^ Harper, Douglas (2012), "leap year", Online Etymology Dictionary
  3. ^ "leap year – Definition of leap year in US English by Oxford Dictionaries". Oxford Dictionaries – English. Retrieved June 3, 2018.
  4. ^ Lerner, Ed. K. Lee; Lerner, Brenda W. (2004). "Calendar". The Gale Encyclopedia of Science. Detroit, MI: Gale.
  5. ^ Introduction to Calendars. (10 August 2017). United States Naval Observatory.
  6. ^ United States Naval Observatory (June 14, 2011), Leap Years
  7. ^ Lerner & Lerner 2004, p. 681.
  8. ^ a b Richards, E. G. (2013), "Calendars", in Urban, S. E.; Seidelmann, P. K., Explanatory Supplement to the Astronomical Almanac (3rd ed.), Mill Valley CA: University Science Books, p. 598, ISBN 9781891389856
  9. ^ Doggett, L.E. (1992), "Calendars", in Seidelmann, P. K., Explanatory Supplement to the Astronomical Almanac (2nd ed.), Sausalito, CA: University Science Books, pp. 580–1
  10. ^ Richards, E. G. (1998), Mapping time: The Calendar and its History, Oxford University Press, pp. 250–1, ISBN 0-19-286205-7
  11. ^ Key, Thomas Hewitt (2013) [1875], Calendarium, University of Chicago
  12. ^ Exodus 23,15 ; Exodus 34,18 ; Deuteronomy 15,1 ; Deuteronomy 15, 13
  13. ^ The Islamic leap year, Time and Date AS, n.d., retrieved February 29, 2012
  14. ^ Leap year trivia you might want to know, GMA News, n.d., retrieved February 29, 2012
  15. ^ Hijri-Shamsi Calendar, Al Islam, 2015, retrieved April 18, 2015
  16. ^ Heydari-Malayeri, M. (2004), A Concise Review of the Iranian Calendar, Paris Observatory, arXiv:astro-ph/0409620, Bibcode:2004astro.ph..9620H
  17. ^ Mikkelson, B.; Mikkelson, D.P. (2010), "The Privilege of Ladies", The Urban Legends Reference Pages, snopes.com
  18. ^ 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).
  19. ^ Felten, E. (February 23, 2008), "The Bissextile b=Beverage", Wall Street Journal
  20. ^ Hallett, S. (February 29, 2012), "Leap Year Proposal: What's The Story Behind It?", Huffington Post, retrieved December 21, 2015
  21. ^ "A Greek Wedding", Anagnosis Books, retrieved January 12, 2012
  22. ^ "Teaching Tips 63", Developing Teachers, retrieved January 12, 2012
  23. ^ Anthony – Leap Year Capital of the World, Time and Date, 2008, retrieved 6 November 2011
  24. ^ "February 29: 29 things you need to know about leap years and their extra day", Mirror, February 28, 2012, retrieved December 7, 2015
  25. ^ Legislative History of the Civil Code of the Republic of China
  26. ^ "Article 121 Civil Code", Part I General Principles of the Republic of China
  27. ^ Age of Majority (Related Provisions) Ordinance (Ch. 410 Sec. 5), Hong Kong Department of Justice, June 30, 1997 (Enacted in 1990).

External links

1704

1704 (MDCCIV)

was a leap year starting on Tuesday of the Gregorian calendar and a leap year starting on Saturday of the Julian calendar, the 1704th year of the Common Era (CE) and Anno Domini (AD) designations, the 704th year of the 2nd millennium, the 4th year of the 18th century, and the 5th year of the 1700s decade. As of the start of 1704, the Gregorian calendar was

11 days ahead of the Julian calendar, which remained in localized use until 1923. In the Swedish calendar it was a leap year starting on Friday, one day ahead of the Julian and ten days behind the Gregorian calendar.

1 BC

Year 1 BC was a common year starting on Friday or Saturday (link will display the full calendar) of the Julian calendar (the sources differ, see leap year error for further information) and a leap year starting on Thursday of the Proleptic Julian calendar. It is also a leap year starting on Saturday, in the Proleptic Gregorian calendar. At the time, it was known as the Year of the Consulship of Lentulus and Piso (or, less frequently, year 753 Ab urbe condita). The denomination 1 BC for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years. The following year is 1 AD in the widely used Julian calendar, which does not have a "year zero".

Adar

Adar (Hebrew: אֲדָר‬ Adar; from Akkadian adaru) is the sixth month of the civil year and the twelfth month of the ecclesiastical year on the Hebrew calendar, roughly corresponding to the month of March in the Gregorian calendar. It is a winter month of 29 days. The Month of Adar in the Holy Scriptures comprises in Esther 09, 21.

In leap years, it is preceded by a 30-day intercalary month named Adar Aleph (Hebrew: אדר א'‬, Aleph being the first letter of the Hebrew alphabet, also known as "Adar Rishon" (First Adar) or "Adar I") and it is then itself called Adar Bet (Hebrew: אדר ב'‬, Bet being the second letter of the Hebrew Alphabet, also known as "Adar Sheni" (Second Adar) or "Adar II"). Occasionally instead of Adar I and Adar II, "Adar" and "Ve'Adar" are used (Ve means 'and' thus: And Adar). Adar I and II occur during February–March on the Gregorian calendar.

Based on a line in the Mishnah declaring that Purim must be celebrated in Adar II in a leap year (Megillah 1:4), Adar I is considered the "extra" month. As a result, someone born in Adar during a non leap year would celebrate his birthday in Adar II during a leap year. However, someone born during either Adar in a leap year will celebrate his birthday during Adar in a non-leap year, except that someone born on 30 Adar I will celebrate his birthday on 1 Nisan in a non-leap year because Adar in a non-leap year has only 29 days.

During the Second Temple period, there was a Jewish custom to make a public proclamation on the first day of the lunar month Adar, reminding the people that they are to prepare their annual monetary offering to the Temple treasury, known as the half-Shekel.

Aquarius (astrology)

Aquarius (♒) is the eleventh astrological sign in the Zodiac, originating from the constellation Aquarius. Under the tropical zodiac, the sun is in Aquarius between about January 21 and about February 20, while under the sidereal Zodiac, the sun is in Aquarius from approximately February 15 to March 14, depending on the leap year.

Aries (astrology)

Aries (♈) (meaning "ram") is the first astrological sign in the zodiac, spanning the first 30 degrees of celestial longitude (0°≤ λ <30°). Under the tropical zodiac, the Sun transits this sign from approximately March 20 to April 21 each year. This time duration is exactly the first month of the Solar Hijri calendar (Hamal/Farvardin/Wray). The symbol of the ram is based on the Chrysomallus, the flying ram that provided the Golden Fleece.According to the tropical system of astrology, the Sun enters the sign of Aries when it reaches the March equinox, which occurs on average on March 20 (by design). Because the Earth takes approximately 365.24 days to go around the Sun, the precise time of the equinox is not the same each year, and generally will occur about six hours later from one year to the next until reset by a leap year. February 29 of a leap year causes that year's vernal equinox to fall about eighteen hours earlier compared with the previous year. From 1800 to 2050 inclusive the vernal equinox date has (or will) range(d) from March 19 at 22:34 UT1 in 2048 to March 21 at 19:15 UT1 in 1903.Under the sidereal zodiac, the sun currently transits Aries from April 15 to 14 May (approximately).

Aries is the first fire sign in the zodiac, the other fire signs being Leo and Sagittarius. Individuals born between these dates, depending on which system of astrology they subscribe to, may be called Arians or Ariens.The equivalent in the Hindu solar calendar is Meṣa.

Ethiopian calendar

The Ethiopian calendar (Amharic: የኢትዮጵያ ዘመን አቆጣጠር; yä'Ityoṗṗya zëmän aḳoṭaṭär) or Eritrean calendar is the principal calendar used in Ethiopia and also serves as the liturgical year for Christians in Eritrea and Ethiopia belonging to the Eritrean Orthodox Tewahedo Church, Ethiopian Orthodox Tewahedo Church, Eastern Catholic Churches, the Coptic Orthodox Church of Alexandria, and Ethiopian-Eritrean Evangelicalism (Ethiopian-Eritrean Protestants in the diaspora usually use both the Ethiopian and Gregorian Calendars for liturgical purposes, by celebrating religious holidays twice). It is a solar calendar which in turn derives from the Egyptian calendar, but like the Julian calendar, it adds a leap day every four years without exception, and begins the year on August 29 or August 30 in the Julian calendar. A gap of 7–8 years between the Ethiopian and Gregorian calendars results from an alternative calculation in determining the date of the Annunciation.

Like the Coptic calendar, the Ethiopic calendar has 12 months of 30 days plus 5 or 6 epagomenal days, which comprise a thirteenth month. The Ethiopian months begin on the same days as those of the Coptic calendar, but their names are in Ge'ez. A 6th epagomenal day is added every 4 years, without exception, on August 29 of the Julian calendar, 6 months before the corresponding Julian leap day. Thus the first day of the Ethiopian year, 1 Mäskäräm, for years between 1900 and 2099 (inclusive), is usually September 11 (Gregorian). However, it falls on September 12 in years before the Gregorian leap year.

February 29

February 29, also known as leap day or leap year day, is a date added to most years that are divisible by 4, such as 2012, 2016, 2020, 2024, and 2028. A leap day is added in various solar calendars (calendars based on the Earth's revolution around the Sun), including the Gregorian calendar standard in most of the world. Lunisolar calendars (whose months are based on the phases of the Moon) instead add a leap or intercalary month.In the Gregorian calendar, years that are divisible by 100, but not by 400, do not contain a leap day. Thus, 1700, 1800, and 1900 did not contain a leap day; neither will 2100, 2200, and 2300. Conversely, 1600 and 2000 did and 2400 will. Years containing a leap day are called leap years. Years not containing a leap day are called common years. February 29 is the 60th day of the Gregorian calendar, in such a year, with 306 days remaining until the end of the year. In the Chinese calendar, this day will only occur in years of the monkey, dragon, and rat.

A leap day is observed because the Earth's period of orbital revolution around the Sun takes approximately 6 hours longer than 365 whole days. A leap day compensates for this lag, realigning the calendar with the Earth's position in the Solar System; otherwise, seasons would occur later than intended in the calendar year. The Julian calendar used in Christendom until the 16th century added a leap day every four years; but this rule adds too many days (roughly 3 every 400 years), making the equinoxes and solstices shift gradually to earlier dates. By the 16th century the vernal equinox had drifted to March 11, and the Gregorian calendar was introduced both to shift it back by omitting several days, and to reduce the number of leap years via the "century rule" to keep the equinoxes more or less fixed and the date of Easter consistently close to the vernal equinox.

Intercalation (timekeeping)

Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.

Leap Year (1924 film)

Leap Year is an American silent comedy film directed by and starring Roscoe Arbuckle. Though produced in 1921, the film was not released in the United States due to Arbuckle's involvement in the Virginia Rappe death scandal; it received its first release in Finland in 1924. The film finally saw an American release of sorts in 1981. Prints held by the UCLA Film and Television Archive and Library of Congress.

Leap Year (1932 film)

Leap Year is a 1932 British comedy film directed by Tom Walls, who co-stars with Anne Grey, Edmund Breon and Ellis Jeffreys. Made at Elstree Studios, it was written by A.R. Rawlinson, and produced by Herbert Wilcox. The film was re-released in 1937.

Leap Year (2010 film)

Leap Year is a 2010 Irish-American romantic comedy film directed by Anand Tucker and written by Harry Elfont and Deborah Kaplan. Loosely based on I Know Where I'm Going, the film stars Amy Adams and Matthew Goode.

The film follows a real estate worker who heads to Ireland to ask her boyfriend to accept her wedding proposal on leap day, when tradition supposedly holds that men cannot refuse a woman's proposal for marriage. Her plans are interrupted by a series of events and are further complicated when she hires an Irish innkeeper to take her to her boyfriend in Dublin.Principal photography took place in County Wicklow, Dublin, County Mayo, and County Galway, with filming taking place in and around the Aran Islands, Connemara, Temple Bar, Georgian Dublin, Wicklow National Park, and Olaf Street, Waterford.

Leap Year premiered in New York City on January 6, 2010 and was released theatrically on January 8, 2010 by Universal Pictures in the United States and on February 28 by Optimum Releasing in Ireland. The film received mostly negative reviews from critics, with many criticising the film’s pacing, plot and limited chemistry between Adams and Goode.

Leap year starting on Friday

A leap year starting on Friday is any year with 366 days (i.e. it includes 29 February) that begins on Friday 1 January and ends on Saturday 31 December. Its dominical letters hence are CB, such as the years 1808, 1836, 1864, 1892, 1904, 1932, 1960, 1988, 2016, 2044, 2072, and 2112 in the Gregorian calendar or, likewise, 2000 and 2028 in the obsolete Julian calendar. Any leap year that starts on Tuesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this leap year occurs in May. Common years starting on Saturday share this characteristic.

Leap year starting on Monday

A leap year starting on Monday is any year with 366 days (i.e. it includes 29 February) that begins on Monday, 1 January, and ends on Tuesday, 31 December. Its dominical letters hence are GF, such as the years 1912, 1940, 1968, 1996, 2024, 2052, 2080, and 2120 in the Gregorian calendar or, likewise, 2008, 2036, and 2064 in the obsolete Julian calendar.

Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in September and December. Common years starting on Tuesday share this characteristic.

Leap year starting on Saturday

A leap year starting on Saturday is any year with 366 days (i.e. it includes 29 February) that begins on Saturday, 1 January, and ends on Sunday, 31 December. Its dominical letters hence are BA, such as the years 1916, 1944, 1972, 2000, and 2028 in the Gregorian calendar or, likewise, 2012 and 2040 in the obsolete Julian calendar. In the Gregorian calendar all centennial leap years start on Saturday; the next such year will be 2400, see below for more.Any leap year that starts on Tuesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this leap year occurs in October. Common years starting on Sunday share this characteristic, but also have another in January. From August of the year that precedes this year until October in this type of year is also the longest period (14 months) that occurs without a Friday the 13th. Common years starting on Tuesday share this characteristic, from July of the year that precedes it to September in that type of year. There are two other ways this 14 month interval can be formed, one involving a common year followed by a leap year and the other a leap year followed by a common year.

Leap year starting on Sunday

A leap year starting on Sunday is any year with 366 days (i.e. it includes 29 February) that begins on Sunday, 1 January, and ends on Monday, 31 December. Its dominical letters hence are AG, such as the years 1888, 1928, 1956, 1984, 2012, 2040, 2068, 2096, 2108, 2136, 2164, and 2192 in the Gregorian calendar or, likewise, 1996 and 2024 in the obsolete Julian calendar.

This leap year has the most occurrences of Friday the 13th. Common years starting on Thursday share this feature. Each instance of Friday the 13th is three months apart in January, April, and July.

Leap year starting on Thursday

A leap year starting on Thursday is any year with 366 days (i.e. it includes 29 February) that begins on Thursday 1 January, and ends on Friday 31 December. Its dominical letters hence are DC, such as the years 1880, 1920, 1948, 1976, 2004, 2032, 2060, and 2088, in the Gregorian calendar or, likewise, 1988, 2016, and 2044 in the obsolete Julian calendar. Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in February and August.

Leap year starting on Tuesday

A leap year starting on Tuesday is any year with 366 days (i.e. it includes 29 February) that begins on Tuesday, 1 January, and ends on Wednesday, 31 December. Its dominical letters hence are FE, such as the years 1884, 1924, 1952, 1980, 2008, 2036, 2064, 2092, and 2104 in the Gregorian calendar or, likewise, 1964, 1992, and 2020 in the obsolete Julian calendar. Any leap year that starts on Tuesday, Friday or Saturday has only one Friday the 13th; The only Friday the 13th in this leap year occurs in June. Common years starting on Wednesday share this characteristic.

Leap year starting on Wednesday

A leap year starting on Wednesday is any year with 366 days (i.e. it includes 29 February) that begins on Wednesday, 1 January, and ends on Thursday, 31 December. Its dominical letters hence are ED, such as the years 1908, 1936, 1964, 1992, 2020, 2048, 2076, and 2116 in the Gregorian calendar or, likewise, 2004 and 2032 in the obsolete Julian calendar.

Any leap year that starts on Monday, Wednesday or Thursday has two Friday the 13ths. This leap year contains two Friday the 13ths in March and November. Common years starting on Thursday share this characteristic, but also have another in February.

Proleptic Julian calendar

The proleptic Julian calendar is produced by extending the Julian calendar backwards to dates preceding AD 8 when the quadrennial leap year stabilized. The leap years that were actually observed between the implementation of the Julian calendar in 45 BC and AD 8 were erratic: see the Julian calendar article for details.

A calendar obtained by extension earlier in time than its invention or implementation is called the "proleptic" version of the calendar. Likewise, the proleptic Gregorian calendar is occasionally used to specify dates before the introduction of the Gregorian calendar in 1582. Because the Julian calendar was used before that time, one must explicitly state that a given quoted date is based on the proleptic Gregorian calendar if that is the case.

Note that the Julian calendar itself was introduced by Julius Caesar, and as such is older than the introduction of the Anno Domini era (or the "Common Era", counting years since the birth of Christ as calculated by Dionysus Exiguus in the 6th century, and widely used in medieval European annals since about the 8th century, notably by Bede). The proleptic Julian calendar uses Anno Domini throughout, including for dates of Late Antiquity when the Julian calendar was in use but Anno Domini wasn't, and for times predating the introduction of the Julian calendar.

Years are given cardinal numbers, using inclusive counting (AD 1 is the first year of the Anno Domini era, immediately preceded by 1 BC, the first year preceding the Anno Domini era, there is no "zeroth" year).

Thus, the year 1 BC of the proleptic Julian calendar is a leap year.

This is to be distinguished from the "astronomical year numbering", introduced in 1740 by French astronomer Jacques Cassini, which considers each New Year an integer on a time axis, with year 0 corresponding to 1 BC, and "year −1" corresponding to 2 BC, so that in this system, Julian leap years have a number divisible by four.

The determination of leap years in the proleptic Julian calendar (in either numbering) is distinct from the question of which years were historically considered leap years during the Roman era, due to the leap year error: Between 45 BC and AD 8, the leap day was somewhat unsystematic. Thus there is no simple way to find an equivalent in the proleptic Julian calendar of a date quoted using either the Roman pre-Julian calendar or the Julian calendar before AD 8. The year 46 BC itself is a special case, because of the historical introduction of the Julian calendar in that year, it was allotted 445 days. Before then, the Roman Republican calendar used a system of intercalary months rather than leap days.

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