Editing Calendar date (section)

{{Short description|Identification of a specific day}}
{{Multiple issues|
{{Missing information|the historical development of calendar dates|date=March 2018}}
{{More citations needed|date=August 2007}}
}}
{{Infobox calendar date today}}
A '''calendar date''' is a reference to a particular [[day]], represented within a [[calendar]] system, enabling a specific day to be unambiguously identified. Simple math can be performed between dates; commonly, the number of days between two dates may be calculated, e.g., "25 {{CURRENTMONTHNAME}} {{CURRENTYEAR}}" is ten days after "15 {{CURRENTMONTHNAME}} {{CURRENTYEAR}}". The date of a particular event depends on the [[time zone]] used to record it. For example, the air attack on Pearl Harbor that began at 7:48&nbsp;a.m. local [[Hawaii–Aleutian Time Zone|Hawaiian time]] (HST) on 7 December 1941 is recorded equally as having happened on 8 December at 3:18&nbsp;a.m. [[Japan Standard Time]] (JST).

A particular day may be assigned a different nominal date according to the calendar used.{{efn|An identifying suffix may be needed where ambiguity may arise, but this may not always be sufficient. For example, the Western (Gregorian) and Eastern (Julian) Christian calendars each use the designation AD but, since [[adoption of the Gregorian calendar|about the middle of the 16th century]], the same day is dated differently by the calendars, despite each using the same format. Consequently the name of the calendar must also be stated. See also [[Old Style and New Style dates]] for the notation used followind a change of civil calendar used.}} The [[de facto standard]] for recording dates worldwide is the [[Gregorian calendar]], the world's most widely used [[civil calendar]].<ref>{{cite book|author-link1=Nachum Dershowitz |last1= Dershowitz | first1= D. |author-link2=Edward Reingold | last2=Reingold |first2= E. M |year= 2008 | title= [[Calendrical Calculations]] | edition = 3rd |publisher= Cambridge University Press | location = Cambridge | page= 45 | quote=The calendar in use today in most of the world is the Gregorian or ''new-style'' calendar designed by a commission assembled by Pope Gregory XIII in the sixteenth century.}}</ref> Many cultures use religious calendars such as the Gregorian ([[Western Christianity|Western Christendom]], AD), the [[Julian calendar]] ([[Orthodoxy#Christianity|Eastern Christendom]], AD), [[Hebrew calendar]] ([[Judaism]], [[Anno Mundi|AM]]), the [[Islamic calendar|Hijri calendars]] ([[Islam]], [[Hijri year|AH]]), or any other of the [[list of calendars |many calendars used around the world]]. [[Regnal year|Regnal calendars]] (that record a date in terms of years since the beginning of the monarch's reign) are also used in some places, for particular purposes. 

In most calendar systems, the date consists of three parts: the (numbered) ''day of the month'', the ''[[month]]'', and the (numbered) ''[[year]]''. There may also be additional parts, such as the ''[[day of the week]]''. Years are counted from a particular starting point called the ''[[epoch]]'', with ''[[era]]'' referring to the span of time since that epoch.{{efn|For details of the [typically retrospective] calculation of the epoch for each calendar, see their respective articles.}} A date without the year may also be referred to as a ''date'' or ''calendar date'' (such as "{{CURRENTDAY}} {{CURRENTMONTHNAME}}" rather than "{{CURRENTDAY}} {{CURRENTMONTHNAME}} {{CURRENTYEAR}}"). As such, it is either shorthand for the current year, or else it defines the day of an annual event such as a birthday on 31 May or Christmas on 25 December.