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Do NOT use this template when the person is dead; consider ((Birth based on age at death)) instead.

This template is used on approximately 5,600 pages and changes may be widely noticed. Test changes in the template's /sandbox or /testcases subpages, or in your own user subpage. Consider discussing changes on the talk page before implementing them.

This template employs intricate features of template syntax.

You are encouraged to familiarise yourself with its setup and parser functions before editing the template. If your edit causes unexpected problems, please undo it quickly, as this template may appear on a large number of pages.
You can conduct experiments, and should test all major changes, in either this template's sandbox, the general template sandbox, or your user space before changing anything here.

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 reliable source states only their age at the time of publication.

Syntax

Typical use

 ((birth based on age as of date | age | year | month | day ))

Code:

((birth based on age as of date|50|2022|11|27))

Result:

1971 or 1972 (age 51–52)

The age, year, and day must be supplied as natural numbers; 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 |noage=yes:

Code:

((birth based on age as of date|50|2022|11|27|noage=1|slash=y))

Result:

1971/1972

Separator

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

To use the / separator, add |slash=yes.

Code:

((birth based on age as of date|50|2022|11|27|slash=yes))

Result:

1971/1972 (age 51–52)

Examples

If, for example, a reference dated July 4, 2022 mentions that someone is 50 years old, that person's birth year and age can be rendered using:

((birth based on age as of date|50|2022|July|4))

The following examples are for a person reported as being 50 years old in 2023

Template code	Result
((birth based on age as of date \| 50 \| 2023 \| 02 \| 27))	1972 or 1973 (age 51)
((birth based on age as of date \| 50 \| 2023 \| February \| 27))	1972 or 1973 (age 51)
((birth based on age as of date \| 50 \| 2023 \| 12 \| 31))	1972 or 1973 (age 50–51)
((birth based on age as of date \| 50 \| 2023 \| Jan \| 1))	1972 or 1973 (age 51–52)
((birth based on age as of date \| 50 \| 2023 \| 12 \| 31 \| noage=1))	1972 or 1973
((birth based on age as of date \| 50 \| 2023 \| Jan \| 1 \| noage=1))	1972 or 1973
((birth based on age as of date \| 50 \| 2023 \| February))	1972 or 1973 (age 50–51)
((birth based on age as of date \| 50 \| 2023 \| Jan))	1972 or 1973 (age 51–52)
((birth based on age as of date \| 50 \| 2023 \| 12))	1972 or 1973 (age 50–51)
((birth based on age as of date \| 50 \| 2023))	1972 or 1973 (age 50–51)

Birth, death and age templates

birth, death, age

Combined BDA template	Description / use
((BirthDeathAge))	Combines functions of ((Birth date)), ((birth-date)), ((birth date and age)), ((birth year and age)), ((death date)), ((death-date)), ((death date and age)), and ((death year and age)).

Birth templates	Description / use
((Birth date))	To display a birth date and related hidden metadata.
((Birth-date))
((Birth date and age))	((Birth date)) with suffix '(age N)'.
((Birth date and age2))	((Birth date and age)) plus age as of a specified date.
((Birth-date and age))	As ((Birth date and age)), but accepts dates in text form ('15 June 1950', 'June 15, 1950', 'June 1950', etc.).
((Birth date and age in years and days))	((Birth date and age)), but with the age displayed in years and days rather than just years.
((Birth year and age))	Year of birth and approximate age.
((Birth based on age as of date))	To display approximate birth year and current age given a particular date (e.g. when a dated reference mentions the age of a person), only works for living people.
((Birth based on age at death))	To display approximate birth year based on age at death, or on age at a specific date if death date isn't known.

Death templates	Description / use
((Death date))	To display a death date and related hidden metadata.
((Death-date))
((Death date and age))	((Death date)) with suffix '(aged N)'; also called with ((event date and age)).
((Death-date and age))	As ((Death date and age)), but accepts dates in text form ('15 June 1950', 'June 15, 1950', 'June 1950', etc.).
((Death date and given age))	To display a death date and specified age.
((Death year and age))	To display a year of, and approximate age at death.

age only

Conventional age templates	Description / use
((Age in years, months, weeks and days))	Number of complete years, months, weeks and days between two dates.
((Age in years, months and days))	Number of complete years, months and days between two dates.
((Age in years and months))	Number of complete years and remaining months between two dates.
((Age in years and days))	Number of complete years and remaining days between two dates.
((Age in years and days nts))	((Age in years and days)) with output formatted for use in number sortable tables.
((Age in decimal years))	Number of years between two dates, rounded to the specified number of decimal places.
((Age in years))	Number of years between two dates.
((Age in years nts))	((Age in years)) with output formatted for use in number sortable tables.
((Age in months))	Number of months between two dates.
((Age in weeks and days))	Number of weeks and days between two dates.
((Age in weeks))	Number of weeks between two dates.
((Age in days))	Age in days between two dates.
((Age in days nts))	((Age in days)) with output formatted for use in number sortable tables.

Reverse-determined age template	Description / use
((Age))	Age based on number of complete years between two dates.
((Age nts))	((Age)) with output formatted for use in number sortable tables.
((Age as of date))	Current age (in years) from a known age at a specified date.
((Age for infant))	Current age for infant: months and days up to one year, years and months up to three years, and years beyond age 3.

start / end dates

Date-focused templates	Description / use
((Start date)) / ((End date))
((Start-date)) / ((End-date))
((Start date and age))
((End date and age))

miscellaneous

Template	Description / use
((OldStyleDate))	Dates in Julian calendar.
((OldStyleDateDY))	As ((OldStyleDate)) but used when Julian / Gregorian dates fall in different years.
((OldStyleDateNY))	As ((OldStyleDate)) but without the year.
((Unidentified for))
((Missing for))

This template calculates the birth year and current age based on the age as of a date.

Template parameters[Edit template data]
This template prefers inline formatting of parameters.
Parameter		Description	Type	Status
Age	`1`	Age of subject at date of reference's publication. Example 55	Number	required
Year	`2`	Year of publication of reference. Example 1950	Number	required
Month	`3`	Month of publication of reference. Example 8 or August	String	suggested
Day	`4`	Day of publication of reference. Example 21	Number	suggested
Hide age	`noage`	Set to a value of 'yes' to display year of birth without the age Default no (i.e., the default is to show the age) Example 1	Boolean	optional
Slash separator	`slash`	Set to 'yes' to separate years with a '/' for tight spaces (e.g., table cells) Suggested values `yes` Default no	Boolean	optional

Redirects

The above documentation is transcluded from Template:Birth based on age as of date/doc.
Editors can experiment in this template's sandbox and testcases pages.
Add categories to the /doc subpage. Subpages of this template.