List of non-standard dates

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Several non-standard dates are used in calendars. Some are used sarcastically, some for scientific or mathematical purposes, and some for exceptional or fictional calendars.

Contents

January 0

January 0 or 0 January is an alternative name for December 31.

In an ephemeris

January 0 is the day before January 1 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 December 31 of the previous year.

January 0 also occurs in the epoch for the ephemeris second, "1900 January 0 at 12 hours ephemeris time". [1] 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. [2]

In software

In Microsoft Excel, the epoch of the 1900 date format is January 0, 1900. [3]

February 30

February 30 or 30 February is a date that does not occur on the Gregorian calendar, where the month of February contains only 28 days, or 29 days in a leap year. February 30 is usually used as a sarcastic date for referring to something that will never happen or will never be done. [4] It also appears in some reform calendars.

Swedish calendar

Swedish calendar for February 1712 Feb1712.jpg
Swedish calendar for February 1712

February 30 was a day that happened in Sweden, 1712. [5]

This occurred because, instead of changing from the Julian calendar to the Gregorian calendar by omitting a block of consecutive days, as had been done in other countries, the Swedish Empire planned to change gradually by omitting all leap days from 1700 to 1740, inclusive. Although the leap day was omitted in February 1700, the Great Northern War 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. [6]

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. [6] [7]

The Swedish conversion to the Gregorian calendar was finally accomplished in 1753, when February 17 was followed by March 1. [6]

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 General Circulation Model is an example. [8]

Fictional calendars

In the works of J. R. R. Tolkien, the Hobbits have developed the Shire Reckoning. According to Appendix D of The Lord of the Rings , 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. [9]

February 30, 1951, is the last night of the world in Ray Bradbury's short story "Last Night of the World". [10]

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 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.[ citation needed ]

Early Julian calendar

The thirteenth-century scholar Johannes de Sacrobosco claimed that in the Julian calendar February had 30 days in leap years from 45 BC until 8 BC, when Augustus allegedly shortened February by one day to give that day to the month of August named after him so that it had the same length as the month of July named after his adoptive father, Julius Caesar. However, all historical evidence refutes Sacrobosco, including dual dates with the Alexandrian calendar. [11]

February 31

February 31 on a tombstone Feb31OnTombstone.jpg
February 31 on a tombstone

February 31 or 31 February is exceptionally used on gravestones when the date is unknown, [12] [ better source needed ] or in at least one case out of, supposedly, superstition (more likely a typo). [13] [14]

It is also used (along with February 32 and February 33) for calculating weather data. [15]

March 0

March 0 or 0 March is an alternative name for the last day of February (February 28, or February 29 in leap years). It is used most often in astronomy, software engineering, [16] [17] and Doomsday algorithm calculations.[ citation needed ]

May 35

May 35 or 35 May is used in mainland China to avoid censorship when referring to the Tiananmen Square protests of 1989, where the official names are strictly censored by the Communist Party, and the event is normally referred to as June 4. [18] It is also used in the title of The 35th of May, or Conrad's Ride to the South Seas , 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's 1970 novel Bomber .

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 of referring to midnight as zero hours.[ citation needed ]

December 32

December 32 or 32 December is the date of Hogswatchnight in Hogfather 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". [19]

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 and the Hanke–Henry Permanent Calendar, contain a 30-day February. The Symmetry454 calendar assigns 35 days to February, May, August, and November, as well as December in a leap year.

See also

Related Research Articles

<span class="mw-page-title-main">Calendar</span> System for organizing the days of year

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, specific day within such a system. A calendar is also a physical record of such a system. A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.

A calendar date is a reference to a particular day represented within a calendar system. The calendar date allows the specific day to be identified. The number of days between two dates may be calculated. For example, "25 October 2022" is ten days after "15 October 2022". The date of a particular event depends on the observed time zone. For example, the air attack on Pearl Harbor that began at 7:48 a.m. Hawaiian time on 7 December 1941 took place at 3:18 a.m. Japan Standard Time, 8 December in Japan.

The Julian calendar, proposed by Julius Caesar in AUC 708, was a reform of the Roman calendar. It took effect on 1 January AUC 709 , by edict. It was designed with the aid of Greek mathematicians and astronomers such as Sosigenes of Alexandria.

A leap year is a calendar year that contains an additional day added to keep the calendar year synchronized with the astronomical year or seasonal year. Because astronomical events and seasons do not repeat in a whole number of days, calendars that have a constant number of days in each year will unavoidably drift over time with respect to the event that the year is supposed to track, such as seasons. By inserting an additional day or month into some years, the drift between a civilization's dating system and the physical properties of the Solar System can be corrected. A year that is not a leap year is a common year.

The Revised Julian calendar, or less formally the new calendar, is a calendar proposed in 1923 by the Serbian scientist Milutin Milanković as a more accurate alternative to both Julian and Gregorian calendars. At the time, the Julian calendar was still in use by all of the Eastern Orthodox Churches and affiliated nations, while the Catholic and Protestant nations were using the Gregorian calendar. Thus, Milanković's aim was to discontinue the divergence between the naming of dates in Eastern and Western churches and nations. It was intended to replace the Julian calendar in Eastern Orthodox Churches and nations. From 1 March 1600 through 28 February 2800, the Revised Julian calendar aligns its dates with the Gregorian calendar, which had been proclaimed in 1582 by Pope Gregory XIII.

<span class="mw-page-title-main">Year</span> Time of planet rotation around the Sun

A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hours of daylight, and, consequently, vegetation and soil fertility. In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter. In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked.

The Julian day is the continuous count of days since the beginning of the Julian period, and is used primarily by astronomers, and in software for easily calculating elapsed days between two events.

<span class="mw-page-title-main">Coptic calendar</span> Egyptian liturgical calendar

The Coptic calendar, also called the Alexandrian calendar, is a liturgical calendar used by the Coptic Orthodox Church and also used by the farming populace in Egypt. It was used for fiscal purposes in Egypt until the adoption of the Gregorian calendar on 11 September 1875. This calendar is based on the ancient Egyptian calendar. To avoid the calendar creep of the latter, a reform of the ancient Egyptian calendar was introduced at the time of Ptolemy III which consisted of adding an extra day every fourth year. However, this reform was opposed by the Egyptian priests, and the reform was not adopted until 25 BC, when the Roman Emperor Augustus imposed the Decree upon Egypt as its official calendar (although initially, namely between 25 BC and AD 5, it was unsynchronized with the newly introduced Julian calendar which had erroneously been intercalating leap days every third year due to a misinterpretation of the leap year rule so as to apply inclusive counting. To distinguish it from the Ancient Egyptian calendar, which remained in use by some astronomers until medieval times, this reformed calendar is known as the Coptic or Alexandrian calendar. Its years and months coincide with those of the Ethiopian calendar but have different numbers and names.

<span class="mw-page-title-main">Date of Easter</span> Calculation of the date of Easter

As a moveable feast, the date of Easter is determined in each year through a calculation known as computus. Easter is celebrated on the first Sunday after the Paschal full moon, which is the first full moon on or after 21 March. Determining this date in advance requires a correlation between the lunar months and the solar year, while also accounting for the month, date, and weekday of the Julian or Gregorian calendar. The complexity of the algorithm arises because of the desire to associate the date of Easter with the date of the Jewish feast of Passover which, Christians believe, is when Jesus was crucified.

<span class="mw-page-title-main">Swedish calendar</span> Calendar in use in Sweden from 1700 to 1712

The Swedish calendar or Swedish style was a calendar in use in Sweden and its possessions from 1 March 1700 until 30 February 1712. It was one day ahead of the Julian calendar and ten days behind the Gregorian calendar. Easter was calculated astronomically, with a minor exception, from 1740 to 1844.

The Darian calendar is a proposed system of timekeeping designed to serve the needs of any possible future human settlers on the planet Mars. It was created by aerospace engineer, political scientist, and space jurist Thomas Gangale in 1985 and named by him after his son Darius. It was first published in June 1986. In 1998 at the founding convention of the Mars Society the calendar was presented as one of two calendar options to be considered along with eighteen other factors to consider for the colonization of Mars.

Dominical letters or Sunday letters are a method used to determine the day of the week for particular dates. When using this method, each year is assigned a letter depending on which day of the week the year starts.

Calendar reform or calendrical reform is any significant revision of a calendar system. The term sometimes is used instead for a proposal to switch to a different calendar design.

The determination of the day of the week for any date may be performed with a variety of algorithms. In addition, perpetual calendars require no calculation by the user, and are essentially lookup tables. A typical application is to calculate the day of the week on which someone was born or a specific event occurred.

The Tabular Islamic calendar is a rule-based variation of the Islamic calendar. It has the same numbering of years and months, but the months are determined by arithmetical rules rather than by observation or astronomical calculations. It was developed by early Muslim astronomers of the second hijra century to provide a predictable time base for calculating the positions of the moon, sun, and planets. It is now used by historians to convert an Islamic date into a Western calendar when no other information is available. Its calendar era is the Hijri year. An example is the Fatimid or Misri calendar.

In astronomy, a Julian year is a unit of measurement of time defined as exactly 365.25 days of 86400 SI seconds each. The length of the Julian year is the average length of the year in the Julian calendar that was used in Western societies until the adoption of the Gregorian Calendar, and from which the unit is named. Nevertheless, because astronomical Julian years are measuring duration rather than designating dates, this Julian year does not correspond to years in the Julian calendar or any other calendar. Nor does it correspond to the many other ways of defining a year.

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 differently so as to make the average calendar year 365.2425 days long, more closely approximating the 365.2422-day 'tropical' or 'solar' year that is determined by the Earth's revolution around the Sun.

<span class="mw-page-title-main">Conversion between Julian and Gregorian calendars</span>

The tables below list equivalent dates in the Julian and Gregorian calendars. Years are given in astronomical year numbering.

<span class="mw-page-title-main">Adoption of the Gregorian calendar</span> Gradual global transition from traditional dating systems to the modern standard

The adoption of the Gregorian Calendar was an event in the modern history of most cultures and societies, marking a change from their traditional dating system to the modern dating system, the Gregorian calendar, that is widely used around the world today. Some states adopted the new calendar from 1582, some did not do so before the early twentieth century, and others did so at various dates between; however a number continue to use a different civil calendar. For many the new style calendar is only used for civil purposes and the old style calendar remains used in religious contexts. Today, the Gregorian calendar is the world's most widely used civil calendar. During – and for some time after – the change between systems, it has been common to use the terms Old Style and New Style when giving dates, to indicate which calendar was used to reckon them.

References

  1. "Leap Seconds". Time Service Department, United States Naval Observatory. Archived from the original on February 28, 2012. Retrieved December 31, 2006.
  2. Ransom, David H. Jr. (November 19, 1989). "Program ASTROCLK: Astronomical Clock and Celestial Tracking Program with Celestial Navigation". p. 110.
  3. Lowe, Scott (May 11, 2007). "How do I... Perform basic formatting in Excel 2003?". TechRepublic .
  4. "Thirty Days Hath February 2000?". About.com. Archived from the original on August 21, 2016. Retrieved November 7, 2013.
  5. "February 30 Was a Real Date". timeanddate.com. Retrieved April 25, 2016.
  6. 1 2 3 Bauer, R. W. (1868). Calender for Aarene fra 601 til 2200. Copenhagen, Denmark: Dansk Historisk Fællesråd (1993 reprint). p. 100. ISBN   87-7423-083-2.
  7. Vallerius, Johannes (1711). Allmanach på åhret effter Christi födelse 1712. Lund, Sweden.
  8. "Hadley Centre: GDT netCDF conventions". MetOffice.com. November 22, 2005. Archived from the original on November 22, 2005. Retrieved March 21, 2017.
  9. Tolkien, J. R. R. (1965). "Appendix D". The Return of the King (2nd ed.). Boston: Houghton Mifflin Co. ISBN   978-0-395-08256-0.
  10. "A Classic Ray Bradbury Esquire Story". esquire.com. June 6, 2012. Retrieved March 21, 2017.
  11. Roscoe Lamont, "The Roman calendar and its reformation by Julius Caesar", Popular Astronomy 27 (1919) 583–595. Sacrobosco's theory is discussed on pages 585–587.
  12. "February 31 On Gravestone". Swampy Acres Farm Blog. December 19, 2018. Archived from the original on December 19, 2018. Retrieved June 13, 2019.
  13. Troy Taylor (2005). Weird Illinois. Sterling Publishing Co., Inc. p. 212. ISBN   9780760759431.
  14. McBride Jacobson, Molly (January 6, 2017). "St. Omer Cemetery Witch Grave". Atlas Obscura.
  15. Everett, J. D. (January 1, 1863). "Description of a method of reducing observations of temperature". American Journal of Science. s2-35 (103): 17–31. Bibcode:1863AmJS...35...17E. doi:10.2475/ajs.s2-35.103.17. S2CID   130637323.
  16. The Astronomical Almanac for the Year 2003: Data for Astronomy, Space Sciences, Geodesy, Surveying, Navigation and Other Applications. U.S. Government Printing Office. 2001. p. K2. Bibcode:2001asal.book.....U. ISBN   978-0-11-887320-8.
  17. Tjia, John S. (2009). Building Financial Models. McGraw Hill Professional. p. 144. ISBN   978-0-07-160890-9.
  18. "China tightens information controls for Tiananmen anniversary". The Age. Australia. Agence France-Presse. June 4, 2009. Retrieved November 3, 2010.
  19. "Lear Fan 2100 (Futura)". The Museum of Flight. 2009. Archived from the original on July 12, 2009. Retrieved November 27, 2009.