Age Calculator is a WordPress plugin that provides a quicktag that will calculate the current age of a person/animal/whatever based on it’s birthdate. Supports changing the verbiage for year(s) and month(s) plus has a multiplier for animals (such as “in dog years”).

Using the quicktag [ agecalc birthdate="1978-01-30 ] will display “31 years” using the default settings. Well, as long as it’s still 2009…  Oh, you’ll need to remove the spaces after the “[" and before the "]“.

Visit the Age Calculator page at the WordPress Plugin Directory for more information.

Testing…
[ agecalc birthdate="1978/01/30" ] => 34 years