View source for Template:Birth based on age as of date/doc

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For a person whose date of birth is unknown, this template estimates the person's birth year and current age based on a given age at a certain date. This is useful when a [[wp:reliable source|reliable source]] states only their age at the time of publication.

{{Notice|This template is appropriate in cases where sources from '''only one''' point in time are available.}}

If you have reason to believe the subject's age has been discussed by sources ''at more than one point in time'', consider not using this template which, by definition, introduces a whole year's worth of error margin. For example, if a reliable source on May 1, 2020 states Mr X is 39 years old and a different source on August 1, 2020 states Mr X is 40 years old, then Mr X must have been born between May 2, 1980 and August 1, 1980. Using this template would suggest a birth year of "1980 or 1981" using the first source, or "1979 or 1980" using the second source. Since the two sources together establish 1980 as the birth year, using this template would be inappropriate.

{{Notice|This template is intended for living people.}}

If the subject has died, please use {{tl|Birth based on age at death}} instead of this template. While {{asof|2024|lc=y}} that template is just a wrapper of this one, this leaves open the possibility to use that template to recategorize the subject. Also, it makes sure you don't forget to suppress the age field.

== Syntax ==
=== Typical use ===
<syntaxhighlight lang="wikitext"> {{birth based on age as of date | age | year | month | day }} </syntaxhighlight>
<div style="margin-left:1.6em;">Code:</div>
<div style="margin-left:3.2em;"><code><nowiki>{{birth based on age as of date|50|</nowiki>{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}<nowiki>}}</nowiki></code></div>
<div style="margin-left:1.6em;">Result:</div>
<div style="margin-left:3.2em;">{{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}}}
</div>
The age, year, and day must be supplied as [[natural number]]s; month can be specified as a natural number as well as by name or abbreviation (e.g. "August" or "Aug").  The [[Gregorian calendar]] is assumed, with no special support provided for [[dual dating]] or the difference between [[Old Style and New Style dates]].

If only the publication year for a source is known, the "day" and "month" fields can be omitted.

=== No age ===
In some contexts—like the lead sentence of a biography—it may be desirable to show only the birth year, and not a person’s age. To suppress the age field, set {{para|noage|yes}}:
<div style="margin-left:1.6em;">Code:</div>
<div style="margin-left:3.2em;"><code><nowiki>{{birth based on age as of date|50|</nowiki>{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}|noage=1<nowiki>}}</nowiki></code></div>
<div style="margin-left:1.6em;">Result:</div>
<div style="margin-left:3.2em;">{{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}|noage=1}}</div>

=== Separator ===
In general, the two possible birth years should be written out as: {{xt|1950 or 1951}}. In contexts which are tight for space, the separator between the two possible years should be a slash: {{xt|1950/1951}}. 

To use the <code>/</code> separator, add {{para|slash|yes}}.
<div style="margin-left:1.6em;">Code:</div>
<div style="margin-left:3.2em;"><code><nowiki>{{birth based on age as of date|50|</nowiki>{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}|slash=yes<nowiki>}}</nowiki></code></div>
<div style="margin-left:1.6em;">Result:</div>
<div style="margin-left:3.2em;">{{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-2}}|{{#expr:12-{{CURRENTMONTH}}+1}}|{{CURRENTDAY}}|slash=yes}}</div>

== Examples ==
If, for example, a reference dated July 4, {{#expr:{{CURRENTYEAR}}-2}} mentions that someone is 50 years old, that person's birth year and age can be rendered using:
<div style="margin-left:1.6em;"><code><nowiki>{{birth based on age as of date|50|</nowiki>{{#expr:{{CURRENTYEAR}}-2}}|July|4}}</code></div>

{| class="plainlinksneverexpand" style="margin-top:0;"
!style="border:1px solid #aaa;background:#dfd;"|
The following examples are for a person reported as being 50 years old in {{#expr:{{CURRENTYEAR}}-1}}
|-
|
{{Aligned table
   |class=wikitable |colstyle=padding-right:1.0em;
   |col1style=font-family:monospace;padding-right:1.0em;
   |row1header=on| {{sans-serif|Template code}} | Result

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTH}}|{{CURRENTDAY}}}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTH}}|{{CURRENTDAY}}}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTHNAME}}|{{CURRENTDAY}}}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTHNAME}}|{{CURRENTDAY}}}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12|31}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12|31}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan|1}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan|1}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12|31|noage{{=}}1}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12|31|noage=1}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan|1|noage{{=}}1}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan|1|noage=1}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTHNAME}}}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|{{CURRENTMONTHNAME}}}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|Jan}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}|12}}

   | {{braces|birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}}}
   |        {{birth based on age as of date|50|{{#expr:{{CURRENTYEAR}}-1}}}}
  }}
|}

{{Birth, death and age templates |BDA}}

<includeonly>{{Sandbox other|
| <!--PLEASE ADD CATEGORIES BELOW THIS LINE: -->
[[Category:Date mathematics templates]] 
}}</includeonly>
<templatedata>
{
	"params": {
		"1": {
			"label": "Age",
			"description": "Age of subject at date of reference's publication.",
			"example": "55",
			"type": "number",
			"required": true
		},
		"2": {
			"label": "Year",
			"description": "Year of publication of reference.",
			"example": "1950",
			"type": "number",
			"required": true
		},
		"3": {
			"label": "Month",
			"description": "Month of publication of reference.",
			"example": "8 or August",
			"type": "string",
			"suggested": true
		},
		"4": {
			"label": "Day",
			"description": "Day of publication of reference.",
			"example": "21",
			"type": "number",
			"suggested": true
		},
		"noage": {
			"label": "Hide age",
			"description": "Set to a value of 'yes' to display year of birth without the age",
			"example": "1",
			"type": "boolean",
			"default": "no (i.e., the default is to show the age)"
		},
		"slash": {
			"label": "Slash separator",
			"description": "Set to 'yes' to separate years with a '/' for tight spaces (e.g., table cells)",
			"suggestedvalues": [
				"yes"
			],
			"type": "boolean",
			"default": "no"
		}
	},
	"description": "This template calculates the birth year and current age based on the age as of a date.",
	"format": "inline",
	"paramOrder": [
		"1",
		"2",
		"3",
		"4",
		"noage",
		"slash"
	]
}
</templatedata>

==Redirects==
* [[Template:Bbad]]
* [[Template:Birth year from age as of date]]
* [[Template:Birth year from age at date]]

==See Also==
* [[Template:Birth date and age]] when exact date of birth is known