Wikipedia:Age calculation templates

Wikipedia uses several templates that self-update every day to keep date and age information current. These are very useful for a dynamic online encyclopedia and save users from having to regularly update that kind of information. However, when using this kind of template, a few things should be kept in mind.

Mentioning "as of" date
In mirrored versions of the site as well as print versions, such statistics will immediately become inaccurate. As such, they should always be accompanied by a note to indicate the date at which it was last correct. The note itself can be made self-updating along with the age calculation template by adding. For more information about self-updating as-of dates, see As of.

When to use templates vs. fixed text
Some of these templates, such as add useful metadata to biography pages, and should be used in the person's infobox or when the information is first needed in the prose. This is true whether the information updates or is fixed.

In lists, however, they should only be used where the self-updating feature is needed. Some of these templates can be complex, and will greatly add to the loading time of a page if used many times. For example, in an article like list of Prime Ministers of Canada by time in office, the template is only used for the incumbent prime minister, and fixed numbers are used for all past prime ministers.

Examples
Common age calculation templates include the following. The age displayed was calculated when the page was last purged and so may not be correct for the current date.

Age

 * Age
 * Age as of date
 * Age at a date - gives the date and the age the individual was at that date
 * Age nts – for use in sortable tables
 * Age in days
 * Age in days nts – for use in sortable tables
 * Age in years - returns a 2-year range; in 2022 someone born in 2000 may be either 21 or 22. Use Age or Years ago with a year parameter to return a single number of years
 * Age in years and days
 * Age in years, months and days
 * Age in months
 * Age in weeks
 * Age in weeks and days
 * Age in years, months, weeks and days
 * Age for infant – displays months and days up to one year, years and months up to three years, and years beyond
 * Years ago

Dates

 * Birth date
 * Birth-date – works with "fuzzy" or ambiguous dates
 * Birth date and age – used on most biographical entries
 * Birth date and age2 – calculates age at a specified date
 * Birth based on age as of date – used when a reference mentions the age of a person as of the date of the reference's publication
 * Birth year and age
 * Death date
 * Death date and age
 * Death year and age
 * BirthDeathAge – combines the functionality of the above six birth and death templates