Age, counted properly
Age is not just this year minus the birth year — it depends on whether the birthday has passed. This calculator does the calendar arithmetic correctly, giving the full years, the months since the last birthday, and the days on top, along with the total number of days lived.
Any two dates
Because the reference date is adjustable, you can find an age at any moment — at a wedding, on a future milestone, on a form's cut-off date. It runs on your device, so a date of birth you enter never leaves the page.