List of non-standard dates

February 31 on a tombstone

Severalnon-standard datesare used incalendarsfor various purposes: some are expressly fictional, some are intended to produce a rhetorical effect (such assarcasm), and others attempt to address a particular mathematical, scientific or accounting requirement or discrepancy within the calendar system.

Historical

January 0

January 0or0 Januaryis an alternative name forDecember 31.January 0 is the day beforeJanuary 1in an annualephemeris.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 asDecember 31of the previous year. January 0 also occurs in theepochfor theephemeris second,"1900 January 0 at 12 hours ephemeris time".1900 January 0 (at Greenwich Mean Noon) was also the epoch used byNewcomb'sTables of the Sun,which became the epoch for theDublin Julian day.

February 30

See also:Swedish calendar

Swedish calendar for February 1712

February 30or30 Februaryis a date that does not occur on theGregorian calendar,where the month ofFebruarycontains only 28 days, or 29 days in aleap year.However, from a historical perspective February 30 has been used at least once and appears in somereform calendars.

The thirteenth-century scholarJohannes de Sacroboscoclaimed that in theJulian calendar,February had 30 days in leap years from 45 BC until 8 BC, whenAugustusallegedly shortened February by one day to give that day to the month ofAugustnamed after him so that it had the same length as the month ofJulynamed after his adoptive father,Julius Caesar.However, all historical evidence refutes Sacrobosco, including dual dates with theAlexandrian calendar.

February 30 was a day that happened inSweden,1712.This occurred because, instead of changing from theJulian calendarto the Gregorian calendar by omitting a block of consecutive days, as had been done in other countries, theSwedish Empireplanned to change gradually by omitting allleap daysfrom 1700 to 1740, inclusive. Although the leap day was omitted in February 1700, theGreat Northern Warbegan 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 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. TheHadley CentreGeneral Circulation Model is an example.

February 31

February 31or31 Februaryis exceptionally used on gravestones when the date is unknown,or, in at least one case, out of supposed superstition (more likely a typo).

May 35

May 35or35 Mayis used in mainland China to avoid censorship when referring to theTiananmen Square protests of 1989,where the official names are strictlycensoredby thenational government,and the event is normally referred to asJune 4.It is also used in the title ofThe 35th of May, or Conrad's Ride to the South Seas,a German children's novel published in 1931.

July 36

A Bengaligraffitiof July 36

In thepopular cultureofBangladesh,July 36or36 Julyrefers to the 5 August 2024, whenPrime ministerSheikh Hasinaresigned and fled the country amid themass revolution.

December 31.5 GMT

See also:Greenwich Mean Time § Ambiguity in the definition of GMT

"December 31.5 GMT"in 1924 almanacs was an instant defined to solve the contrast between two different conventions in defining thecivil timeof referring to midnight as zero hours.

December 32, 1980

TheLearAvia Lear Fanaircraft 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 a sympathetic government official recorded the date as "December 32, 1980".

Software

Several non-standard dates are also used in programming. InMicrosoft Excel,theepochof the 1900 date format is January 0, 1900.February 31 is used (along with February 32 and February 33) for calculating weather data, andMarch 0or0 Marchis used often insoftware engineering.

Other uses

March 0 is used inastronomy.

Fictional calendars

In the works ofJ. R. R. Tolkien,theHobbitshave developed theShire Reckoning.According to Appendix D ofThe Lord of the Rings,this calendar has arranged the year in 12 months of 30 days each. The month the Hobbits callSolmathis rendered in the text asFebruary,and therefore the date February 30 exists in the narrative.

February 30, 1951, is the last night of the world inRay Bradbury's short story "Last Night of the World".

June 31is a fictional date in the Soviet film31 June.It is also the date of a fictional RAF raid on Germany inLen Deighton's 1970 novelBomber.

December 32or32 Decemberis the date of Hogswatchnight inHogfatherby Terry Pratchett. It has also been used as atitle for various works.

The children's bookPlease Try to Remember the First of Octember!byDr. Seussnarrates many delightful things which are supposed to happen starting on the first day of the fictional month of Octember.

In popular culture

March 0 is used inDoomsday algorithmcalculations.March 2was celebrated as February 30 byLin-Manuel MirandaandWeird Al Yankovicfor the release date of Yankovic's "TheHamiltonPolka ".

In November 2010 it was discovered that aHanshin Tigerswall calendar incorrectly included the dateNovember 31.Fans who had bought the calendar were given a sticker to cover up the date, and reprinted calendars were sent.

In the episode "94 Meetings"of the sitcomParks and Recreation,Ron Swanson is forced to deal with 94 meetings in a single day because his assistant, April, scheduled them all for March 31st (instead of the common fake date of February 31st), mistakenly believing it was not a real date.

Soul bandBlack Pumasincluded a song named "OCT 33" on theirGrammy-nominated 2019eponymous album.

The 1998 French-language filmAugust 32nd on Earthwas written and directed byDenis Villeneuve,and was his feature film directoral debut.

InBangladeshipopular culture,August 5,2024 was celebrated asJuly 36,whenPrime ministerSheikh Hasinaresigned and fled the country amid themass uprising,in remembrance of thosediedin thestudents' job quota reform movementon the month ofJuly 2024.

Reform calendars

Because evening out the lengths of the months is part of the rationale forreforming the calendar,some reform calendars, such as theWorld Calendarand theHanke–Henry Permanent Calendar,contain a 30-day February. TheSymmetry454calendar assigns 35 days to February, May, August, and November, as well as December in a leap year.

See also

• Ides of March
• List of calendars
• Time formatting and storage bugs
• System time
• Tibb's Eve,a day said to occur neither before nor after Christmas
• Undecimber

References

• The Oxford Companion to the Year.Bonnie Blackburn & Leofranc Holford-Strevens. Oxford University Press 1999.ISBN0-19-214231-3.pp. 98–99.

External links

• Months in Order
• 30 days in February 1712
• Change of calendars - Sweden (in Swedish)
• 30 Februaryon Tolkien Gateway