User:PL290/MoS/Chronological items

Precise language
Avoid statements that will date quickly, except on pages that are regularly updated, such as those that cover current events. Avoid such items as now and soon (unless their intended meaning is clear), currently and recently (except on rare occasions where they are not redundant), or phrases such as in modern times and the sixties. Instead, when writing about past events use more precise phrases such as during the 1990s, or in August 1969. For future and current events use phrases such as as of July 2024, or since the start of 2005 which indicate the time-dependence of the information to the reader.

To assist editors in keeping the information up to date, statements about future and current events may be used in conjunction with the as of technique. This is done using the as of template to tag information that may become dated quickly: produces the text  and categorizes the article appropriately. This technique is not an alternative to using precise language. For instance, one should not replace since the start of 2005 with because some information (the start of 2005) would be lost; instead, use either the plain text or a more advanced feature of  such as.

Time of day
Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (1:38:09 pm and 13:38:09).
 * 12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, which are spaced (2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Noon and midnight are used rather than 12 pm and 12 am; whether midnight refers to the start or the end of a date will need to be specified unless this is clear from the context.
 * 24-hour clock times have no a.m., p.m., noon or midnight suffix. Discretion may be used as to whether the hour has a leading zero (08:15 or 8:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 24:00 to midnight at the end of a date but should not be used for the first hour of the next day (e.g., use 00:10 for ten minutes after midnight, not 24:10).

Time of day is normally expressed in figures rather than being spelled out. For details, and information on time intervals (e.g., 5 minutes), see Numbers as figures or words, below.

Day, month and season names
See Manual of Style (capital letters)

Dates

 * Wikipedia does not use ordinal suffixes, articles, or leading zeros. Wikipedia does not insert a comma between month and year; however, a comma is required between day and year.


 * {| class="wikitable"

!style="text-align:left"| Incorrect !style="text-align:left"| Correct
 * 9th June the 9th of June || 9 June
 * June 9th || June 9
 * June, 2001 || June 2001
 * 9 June, 2001 09 June 2001 || 9 June 2001
 * June 9 2001 June 09, 2001|| June 9, 2001
 * }
 * 9 June, 2001 09 June 2001 || 9 June 2001
 * June 9 2001 June 09, 2001|| June 9, 2001
 * }
 * June 9 2001 June 09, 2001|| June 9, 2001
 * }


 * If a date range is abbreviated, use the formats 5–7 January 1979 or January 5–7, 2002, with an unspaced en-dash.
 * A night may be expressed in terms of the two contiguous dates using a slash (the bombing raids of the night of 30/31 May 1942).
 * Do not use date formats such as 03/04/2005, as they are ambiguous (it could refer to 3 April or to March 4). For consistency, do not use such formats even if the day number is greater than 12.
 * YYYY-MM-DD style dates (1976-05-31) are uncommon in English prose, and should not be used within sentences. However, they may be useful in long lists and tables for conciseness. (For sorting in tables consider using or .) Because it might be thought to be following the ISO 8601 standard, this format should only be used for dates expressed in the Gregorian calendar and for the years from 1583 through 9999.

Full date formatting
In general, the following formats are acceptable:

Date formatting in an article is governed by the following three guidelines.
 * Month before day: February 14 and February 14, 1990 (comma required)
 * Day before month: 14 February and 14 February 1990 (no comma)

Format consistency

 * Dates in article body text should all have the same format.
 * Dates in article references should all have the same format.

These requirements apply to dates in general prose and reference citations, but not to dates in quotations or titles.

Strong national ties to a topic

 * Articles on topics with strong ties to a particular English-speaking country should generally use the more common date format for that nation. For the U.S. this is month before day; for most others it is day before month. Articles related to Canada may use either format consistently.
 * In certain subject areas the customary format may differ from the usual national one: for example, articles on the modern U.S. military use day before month, in accordance with usage in that field.

Retaining the existing format

 * If an article has evolved using predominantly one format, the whole article should conform to it, unless there are reasons for changing it based on strong national ties to the topic.
 * In the early stages of writing an article, the date format chosen by the first major contributor to the article should be used, unless there is reason to change it based on strong national ties to the topic. Where an article that is not a stub shows no clear sign of which format is used, the first person to insert a date is equivalent to "the first major contributor".

Dates of birth and death
At the start of an article on an individual, his or her dates of birth and death are provided. For example: "Charles Darwin (12 February 1809 – 19 April 1882) was a British ..." (En dashes are preceded by a non-breaking space per WP:DASH, except between year-pairs.)


 * For an individual still living: "Serena Williams (born September 26, 1981) ...", not "... (September 26, 1981 –) ..."
 * When only the years are known: "Socrates (470–399 BC) was..."
 * When the year of birth is completely unknown, it should be extrapolated from earliest known period of activity: "Offa of Mercia (before 734 – 26 July 796) ..."
 * When the year of birth is known only approximately: "Genghis Khan (c. 1162 – August 18, 1227) ..."
 * When the years of both birth and death are known only approximately: "Dionysius Exiguus (c. 470 – c. 540) ..."
 * When the date of death is completely unknown, it should be extrapolated from last known period of activity: "Robert Menli Lyon (1789 – after 1863) ..."
 * When the reign of a sovereign is uncertain: "Rameses III (reigned c. 1180 BCE – c. 1150 BCE) ..."
 * When the individual is known to have been alive (flourishing) at certain dates,  is used in articles to link to floruit, in case the meaning is not familiar: "Osmund (fl. 760–772) ..."
 * When the individual is known to have been alive as early as about 660, and to have died in 685: "Aethelwalh (fl. c. 660–685) ..."

In biographical infobox templates, provide age calculation and microformat compatibility with birth date and age for living people and death date and age (alongside birth date) for the deceased when the full birth or death date, respectively, is precisely known in the Gregorian calendar (adopted in 1752 in most English-speaking countries). See the documentation for those templates in order to use them properly.

Other date ranges
Dates that are given as ranges should follow the same patterns as given above for birth and death dates.

Linking and autoformatting of dates
Dates should not be linked purely for the purpose of autoformatting (even though linking was previously recommended). Dates should only be linked when they are germane and topical to the subject, as discussed at Linking.

Longer periods

 * Months are expressed as whole words (February, not 2), except in the ISO 8601 format; unlike in some other languages, names of months (and of days of the week) are capitalized in English. Abbreviations such as Feb are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of between a month and a year (April 2000, not April of 2000).


 * Seasons. Because the seasons are not the same everywhere in the world, it is generally preferable not to use season names to denote a time of year. Instead use a date or month, or a globally-applicable term such as: in early 1990, in the second quarter of 2003, around September. Use a season name only if there is a logical connection (the autumn harvest). Seasons are normally spelled with a lower-case initial.


 * Years
 * Years are normally expressed in digits. Avoid inserting the words the year before the digits (1995, not the year 1995), unless the meaning would otherwise be unclear.
 * Year ranges, like all ranges, are separated by an en dash, not a hyphen or slash: 2005–06 is a two-year range, whereas 2005/06 is a period of twelve months or less such as a sports season or a financial year. A closing CE or AD year is normally written with two digits (1881–86) unless it is in a different century from that of the opening year (1881–1986). The full closing year is acceptable, but abbreviating it to a single digit (1881–6) or three digits (1881–886) is not. A closing BCE or BC year is given in full (2590–2550 BCE). While one era signifier at the end of a date range requires an unspaced en dash (12–5 BC), a spaced en dash is required when a signifier is used after the opening and closing years (5 BC – AD 29).
 * To indicate around, approximately, or about, the abbreviations c. and ca. are preferred over circa, approximately, or approx., and are spaced (c. 1291). Do not use a question mark for this function (1291?), as this may imply to the reader an uncertainty on the part of Wikipedia editors rather than on the part of reliable historians.
 * Decades
 * Decades as such contain neither an apostrophe nor the suffix -ies (the 1980s, not the 1980's, not the 1980-ies). The two-digit form is never used in reference to the decade as a time span per se.
 * The two-digit form, to which a preceding apostrophe should be added, is used only in reference to a social era or cultural phenomenon that roughly corresponds to and is said to define a decade, and only if it is used in a sourceable stock phrase (the Roaring '20s, the Gay '90s), or when there is a notable connection between the period and what is being discussed in the sentence (a sense of social justice informed by '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971). Such an abbreviation should not be used if it would be redundant (' 80s Reaganomics) or if it does not have a clear cultural significance and usage (the '10s).
 * Centuries and millennia
 * For purposes of written style, the English Wikipedia does not recognize a year 0. Therefore, for dates AD (or CE) the 1st century was 1–100, the 17th century was 1601–1700, and the second millennium was 1001–2000; for dates BC (or BCE) the 1st century was 100–1; the 17th century was 1700–1601, and the second millennium was 2000–1001.
 * Forms such as the 1700s are normally best avoided (although the difference in meaning should be noted: the 1700s is 1700–1799, whereas the 18th century is 1701–1800).

Year numbering systems

 * Years are numbered according to the traditional western Dionysian era (Common Era).
 * AD and BC are the traditional ways of referring to these eras. CE and BCE are becoming more common in academic and some religious writing. No preference is given to either style.
 * Do not use CE or AD unless the date would be ambiguous without it. E.g., "The Norman Conquest took place in 1066." not 1066 CE or AD 1066.
 * BCE and CE or BC and AD are written in upper case, unspaced, and without periods (full stops).
 * Use either the BC-AD or the BCE-CE notation, but not both in the same article. AD may appear before or after a year (AD 106, 106 AD); the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
 * Do not change from one style to another unless there is substantial reason for the change, and consensus for the change with other editors.
 * Uncalibrated (bce) radiocarbon dates: Some source materials will indicate whether a date is calibrated or not simply by a change in capitalization; this is often a source of confusion for the unwary reader. Do not give uncalibrated radiocarbon dates (represented by the lower-case bce unit, occasionally bc or b.c. in some sources), except in directly quoted material, and even then include a footnote, a square-bracketed editor's note [like this], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognize the distinction between bce and BCE / BC.
 * Abbreviations indicating long periods of time ago—such as BP (before present), as well as various annum-based units such as ka (kiloannum), Ma (megaannum) and Ga (gigaannum) are given as full words on first occurrence. Where source quotations use the abbreviations tya or kya (thousand years ago), mya (million years ago), or bya (billion years ago) this should be explained to the reader, as in a measured Libby radiocarbon date of 35.1 mya [million years ago] had to be calibrated ... The tya/kya, mya and bya symbols are deprecated in some fields such as geophysics and geology, but remain common in others, such as anthropology.
 * BP: Do not convert other notations to BP unless you are certain of what you are doing. In some contexts the unit BP is actually defined as "years before January 1, 1950", not "years before the literal present", and the conversion may introduce an error if the date being converted is not a wide approximation (18,000 BP) but a more narrow one or an actual known year. BP years are given as 18,000 BP or spelled out as 18,000 years before present (not 18,000 YBP, 18,000 before present, 18,000 years before the present, or similar.)

Calendars
Dates can be given in any appropriate calendar, as long as the date in either the Julian or Gregorian calendars is provided, as described below. For example, an article on the early history of Islam may give dates in both Islamic and Julian calendars. Where a calendar other than the Julian or Gregorian is used, this must be clear to readers.
 * Current events are given in the Gregorian calendar.
 * Dates before the adoption of the Gregorian calendar on 15 October 1582 are normally given in the Julian calendar. The Julian day and month should not be converted to the Gregorian calendar, but the start of the Julian year should be assumed to be 1 January (see below for more details).
 * Dates for Roman history before 45 BC are given in the Roman calendar, which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
 * The Julian or Gregorian equivalent of dates in early Egyptian and Mesopotamian history is often debatable. Follow the consensus of reliable sources, or indicate their divergence.
 * Dates of events in countries using the Gregorian calendar are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 14 September 1752, and Russia from 14 February 1918 (see the Gregorian calendar article).

The dating method used should follow that used by reliable secondary sources. If the reliable secondary sources disagree, choose the most common used by reliable secondary sources and note the usage in a footnote.

At some places and times, dates other than 1 January were used as the start of the year. The most common English-language convention was the Annunciation Style used in Britain and its colonies, in which the year started on 25 March, Annunciation Day; see the New Year article for a list of other styles. 1 January is assumed to be the opening date for years; if there is reason to use another start-date, this should be stated.

If there is a need to mention Old Style or New Style dates in an article (as in the Glorious Revolution), a footnote should be provided on the first usage, stating whether the New Style refers to a start of year adjustment or to the Gregorian calendar (it can mean either).

Time zones
When writing a date, first consider where the event happened and use the time zone there. For example, the date of the Attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). If it is difficult to judge where, consider what is significant. For example, if a vandal based in Japan attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. If known, include the UTC date and time of the event in the article, indicating that it is UTC.