Age and Event Calculators

How age is counted

Age is counted the way people actually count it: whole years since the birth date, then whole months since that anniversary, then the days left over. Nothing is averaged or divided, so the answer always matches the birthday you would celebrate.

This is why the exact age will not equal the total days divided by 365. Years are not all the same length, and dividing by 365.25 is an approximation that gets the answer slightly wrong in most years.

Leap-year birthdays

Somebody born on 29 February has a real birthday only in leap years. In other years an anniversary has to be chosen, and there is no single worldwide rule:

• 28 February — the usual convention in the UK and the United States, and the one these calculators use.
• 1 March — used for some legal purposes in parts of Europe and Asia, on the basis that a full year has not elapsed until March.

For birthdays and celebrations either is fine. If the exact date decides eligibility for something — a licence, a pension, a school year — check which rule applies, because a single day can matter.

Working out a date of birth from an age

Set the age calculator to the date the age was recorded and work backwards. Remember that an age of "36" covers a full year of possible birth dates, so it narrows things down rather than pinning them exactly.

Countdowns to anything annual

The birthday countdown works for any recurring annual date, not just birthdays: wedding anniversaries, work anniversaries, renewal dates and repeating deadlines all behave the same way. Enter the original date and it counts to the next anniversary.

A note on time zones

Ages and countdowns are calculated in whole calendar days, measured from today in your own time zone. That is why a countdown here may differ by a day from a site that calculates in UTC — particularly in the evening if you are west of Greenwich.