Several non-standard dates are used in

calendars A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a ph ...

. Some are used sarcastically, some for scientific or mathematical purposes, and some for exceptional or fictional calendars.

January 0

January 0 or 0 January is an alternative name for

December 31 It is known by a collection of names including: Saint Sylvester's Day, New Year's Eve or Old Years Day/Night, as the following day is New Year's Day. It is the last day of the year; the following day is January 1, the first day of the following ...

In an ephemeris

January 0 is the day before

January 1 January 1 or 1 January is the first day of the year in the Gregorian Calendar. There are 364 days remaining until the end of the year (365 in leap years). This day is also known as New Year's Day since the day marks the beginning of the yea ...

in an annual ephemeris. It keeps the date in the year for which the ephemeris was published, thus avoiding any reference to the previous year, even though it is the same day as

of the previous year. January 0 also occurs in the

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

for the ephemeris second, "1900 January 0 at 12 hours ephemeris time". 1900 January 0 (at Greenwich Mean Noon) was also the epoch used by Newcomb's ''Tables of the Sun'', which became the epoch for the Dublin Julian day.

In software

Microsoft Excel Microsoft Excel is a spreadsheet developed by Microsoft for Microsoft Windows, Windows, macOS, Android (operating system), Android and iOS. It features calculation or computation capabilities, graphing tools, pivot tables, and a macro (comp ...

, the

of the 1900 date format is January 0, 1900.

February 30

February 30 or 30 February is a date that does not occur on the

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years dif ...

, where the month of

February February is the second month of the year in the Julian and Gregorian calendars. The month has 28 days in common years or 29 in leap years, with the 29th day being called the ''leap day''. It is the first of five months not to have 31 days (th ...

contains only 28 days, or 29 days in a

leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year or s ...

. February 30 is usually used as a sarcastic date for referring to something that will never happen or will never be done. It also appears in some reform calendars.

Swedish calendar

February 30 was a day that happened in Sweden, 1712. This occurred because, instead of changing from the

Julian calendar The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandr ...

to the Gregorian calendar by omitting a block of consecutive days, as had been done in other countries, the

Swedish Empire The Swedish Empire was a European great power that exercised territorial control over much of the Baltic region during the 17th and early 18th centuries ( sv, Stormaktstiden, "the Era of Great Power"). The beginning of the empire is usually ta ...

planned to change gradually by omitting all

leap day February 29, also known as leap day or leap year day, is a date added to leap years. 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 m ...

s from 1700 to 1740, inclusive. Although the leap day was omitted in February 1700, the

Great Northern War The Great Northern War (1700–1721) was a conflict in which a coalition led by the Tsardom of Russia successfully contested the supremacy of the Swedish Empire in Northern, Central and Eastern Europe. The initial leaders of the anti-Swed ...

began later that year, diverting the attention of the Swedes from their calendar so that they did not omit leap days on the next two occasions; 1704 and 1708 remained leap years. To avoid confusion and further mistakes, the Julian calendar was restored in 1712 by adding an extra leap day, thus giving that year the only known actual use of February 30 in a calendar. That day corresponded to February 29 in the Julian calendar and to March 11 in the Gregorian calendar. The Swedish conversion to the Gregorian calendar was finally accomplished in 1753, when February 17 was followed by March 1.

Artificial calendars

Artificial calendars may also have 30 days in February. For example, in a climate model the statistics may be simplified by having 12 months of 30 days. The

Hadley Centre The Met Office Hadley Centre — named in honour of George Hadley — is one of the United Kingdom's leading centres for the study of scientific issues associated with climate change. It is part of, and based at the headquarters of the Met Off ...

General Circulation Model is an example.

Fictional calendars

In the works of

J. R. R. Tolkien John Ronald Reuel Tolkien (, ; 3 January 1892 – 2 September 1973) was an English writer and philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was the Rawlins ...

, the

Hobbits Hobbits are a fictional race of people in the novels of J. R. R. Tolkien. About half average human height, Tolkien presented hobbits as a variety of humanity, or close relatives thereof. Occasionally known as halflings in Tolkien's writings, ...

have developed the

Shire Reckoning The Shire is a region of J. R. R. Tolkien's fictional Middle-earth, described in ''The Lord of the Rings'' and other works. The Shire is an inland area settled exclusively by hobbits, the Shire-folk, largely sheltered from the goings-on in the ...

. According to Appendix D of ''

The Lord of the Rings ''The Lord of the Rings'' is an epic high-fantasy novel by English author and scholar J. R. R. Tolkien. Set in Middle-earth, intended to be Earth at some time in the distant past, the story began as a sequel to Tolkien's 1937 children's boo ...

'', this calendar has arranged the year in 12 months of 30 days each. The month the Hobbits call ''Solmath'' is rendered in the text as ''February'', and therefore the date February 30 exists in the narrative. February 30, 1951, is the last night of the world in

Ray Bradbury Ray Douglas Bradbury (; August 22, 1920June 5, 2012) was an American author and screenwriter. One of the most celebrated 20th-century American writers, he worked in a variety of modes, including fantasy, science fiction, horror, mystery fictio ...

's short story "Last Night of the World".

Myths

Soviet calendar

Although many sources state that 30-day months were used in the Soviet Union for part or all of the period from 1929 to 1940, the

Soviet calendar The Soviet calendar was a modified Gregorian calendar that was used in Soviet Russia between 1918 and 1940. Several variations were used during that time. The Gregorian calendar, under the name "Western European calendar", was implemented in Sov ...

with 5- and 6-day weeks was used only for assigning workdays and days of rest in factories. The Gregorian calendar (since 1918) remained for everyday use: surviving physical calendars from that period show only the irregular months of the Gregorian calendar, including a 28- or 29-day February, suggesting there was never a February 30 in the Soviet Union.

Early Julian calendar

The thirteenth-century scholar

Johannes de Sacrobosco Johannes de Sacrobosco, also written Ioannes de Sacro Bosco, later called John of Holywood or John of Holybush ( 1195 – 1256), was a scholar, monk, and astronomer who taught at the University of Paris. He wrote a short introduction to the Hi ...

claimed that in the

February had 30 days in leap years from 45 BC until 8 BC, when

Augustus Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian, was the first Roman emperor; he reigned from 27 BC until his death in AD 14. He is known for being the founder of the Roman Pri ...

allegedly shortened February by one day to give that day to the month of

August August is the eighth month of the year in the Julian and Gregorian calendars, and the fifth of seven months to have a length of 31 days. Its zodiac sign is Leo and was originally named ''Sextilis'' in Latin because it was the 6th month in ...

named after him so that it had the same length as the month of

July July is the seventh month of the year in the Julian and Gregorian calendars and is the fourth of seven months to have a length of 31 days. It was named by the Roman Senate in honour of Roman general Julius Caesar in 44 B.C., it being the mont ...

named after his adoptive father,

Julius Caesar Gaius Julius Caesar (; ; 12 July 100 BC – 15 March 44 BC), was a Roman general and statesman. A member of the First Triumvirate, Caesar led the Roman armies in the Gallic Wars before defeating his political rival Pompey in a civil war, and ...

. However, all historical evidence refutes Sacrobosco, including dual dates with the Alexandrian calendar.

February 31

February 31 or 31 February is exceptionally used on gravestones when the date is unknown, or in at least one case out of, supposedly, superstition (more likely a typo). It is also used (along with February 32 and February 33) for calculating weather data.

March 0

March 0 or 0 March is an alternative name for the last day of February ( February 28, or

February 29 February 29, also known as leap day or leap year day, is a date added to leap years. 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 mos ...

s). It is used most often in

astronomy Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...

software engineering Software engineering is a systematic engineering approach to software development. A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term '' ...

, and Doomsday algorithm calculations.

May 35

May 35 or 35 May is used in mainland China to avoid censorship when referring to the

Tiananmen Square protests of 1989 The Tiananmen Square protests, known in Chinese as the June Fourth Incident (), were student-led demonstrations held in Tiananmen Square, Beijing during 1989. In what is known as the Tiananmen Square Massacre, or in Chinese the June Fourth ...

, where the official names are strictly censored by the

Communist Party A communist party is a political party that seeks to realize the socio-economic goals of communism. The term ''communist party'' was popularized by the title of ''The Manifesto of the Communist Party'' (1848) by Karl Marx and Friedrich Engels. A ...

, and the event is normally referred to as

June 4 Events Pre-1600 *1411 – King Charles VI granted a monopoly for the ripening of Roquefort cheese to the people of Roquefort-sur-Soulzon as they had been doing for centuries. * 1561 – The steeple of St Paul's, the medieval cathedr ...

. It is also used in the title of ''

The 35th of May, or Conrad's Ride to the South Seas ''The 35th of May, or Conrad's Ride to the South Seas'' (''Der 35. Mai oder Konrad reitet in die Südsee'' in German, its original language) is a novel by Erich Kästner, first published in 1931. Unlike most of Kästner's other works - set in a ...

'', a German children's novel published in 1931.

June 31

June 31 is a fictional date in the Soviet film '' 31 June''. It is also the date of a fictional RAF raid on Germany in

Len Deighton Leonard Cyril Deighton (; born 18 February 1929) is a British author. His publications have included cookery books, history and military history, but he is best known for his spy novels. After completing his national service in the Royal Air Fo ...

's 1970 novel ''

Bomber A bomber is a military combat aircraft designed to attack ground and naval targets by dropping air-to-ground weaponry (such as bombs), launching aerial torpedo, torpedoes, or deploying air-launched cruise missiles. The first use of bombs dropped ...

''.

December 31.5 GMT

"December 31.5 GMT" in 1924 almanacs was an instant defined to solve the contrast between two different conventions in defining the

civil time In modern usage, civil time refers to statutory time as designated by civilian authorities. Modern civil time is generally national standard time in a time zone at a fixed offset from Coordinated Universal Time (UTC), possibly adjusted by dayligh ...

of referring to midnight as zero hours.

December 32

December 32 or 32 December is the date of Hogswatchnight in ''

Hogfather ''Hogfather'' is the 20th ''Discworld'' novel by Terry Pratchett, and a 1997 British Fantasy Award nominee. It was first released in 1996 and published by Victor Gollancz. It came in 137th place in The Big Read, a BBC survey of the most loved ...

'' by Terry Pratchett. It has also been used as a title for various works.

December 32, 1980

The LearAvia Lear Fan aircraft test flight had British government "funding that expired at the end of that year." After the cancellation of a planned test flight on December 31, 1980, due to technical issues, the first prototype made its maiden flight on January 1, 1981, but the date was officially recorded by sympathetic British government officials as "December 32, 1980".

Reform calendars

Because evening out the months is a part of the rationale for reforming the calendar, some reform calendars, such as the

World Calendar The World Calendar is a proposed reform of the Gregorian calendar created by Elisabeth Achelis of Brooklyn, New York in 1930. Features The World Calendar is a 12-month, perennial calendar with equal quarters. Each quarter begins on a Sunday ...

and the

Hanke–Henry Permanent Calendar The Hanke–Henry Permanent Calendar (HHPC) is a proposal for calendar reform. It is one of many examples of leap week calendars, calendars that maintain synchronization with the solar year by intercalating entire weeks rather than single days. I ...

, contain a 30-day February. The

Symmetry454 The Symmetry454 calendar (Sym454) is a proposal for calendar reform created by Irv Bromberg of the University of Toronto, Canada. It is a perennial solar calendar that conserves the traditional month pattern and 7-day week, has symmetrical equal ...

calendar assigns 35 days to February, May, August, and November, as well as December in a leap year.

References

* ''The Oxford Companion to the Year''. Bonnie Blackburn & Leofranc Holford-Strevens. Oxford University Press 1999. . Pages 98–99.

External links

30 days in February 171230 February
on Tolkien Gateway {{DEFAULTSORT:Non-standard dates February 1712 in Sweden English-language idioms January 00 December 0 (number)

Dates Date or dates may refer to: *Date (fruit), the fruit of the date palm (''Phoenix dactylifera'') Social activity *Dating, a form of courtship involving social activity, with the aim of assessing a potential partner **Group dating * Play date, a ...