How are months counted?

By calendar, not by an average length. From 31 January to 1 March is one month and one day, because the month is counted first and the remaining days after it — which is how people actually mean it.

Are leap years handled?

Yes. The day count follows the real calendar, including 29 February.

Does it handle leap years correctly?

Yes. It counts calendar years, months and days rather than dividing by 365, so a birthday on 29 February behaves properly.

Can I work out the gap between two other dates?

Yes — change both dates. Age from a birth date is just the common case of the difference between two days.

Age Calculator

Exact age in years, months and days, plus the gap between any two dates.

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How to use Age Calculator

Enter a date of birth.
Optionally enter a second date to measure to, instead of today.
Read the exact age in years, months and days.

How age is counted here

Calendar years, then whole months, then the days left over — the way a person says their age, and the way official forms expect it.

Dividing days by 365 is the common shortcut and it drifts: it loses a day every leap year, so someone 40 years old comes out ten days young.

A birthday on 29 February counts as having passed on 28 February in a common year, which is the convention most countries use for legal age.

Ages that matter, in most of Europe

Age	Usually means
16	Part-time work in many EU countries
18	Legal majority across the EU and UK
21	Some visa and car-hire minimums
25	Cheaper car insurance bands begin
67	State pension age in Germany, rising

Check the rule that applies where you are — these are the common cases, not law.

Questions

How are months counted?: By calendar, not by an average length. From 31 January to 1 March is one month and one day, because the month is counted first and the remaining days after it — which is how people actually mean it.
Are leap years handled?: Yes. The day count follows the real calendar, including 29 February.
Does it handle leap years correctly?: Yes. It counts calendar years, months and days rather than dividing by 365, so a birthday on 29 February behaves properly.
Can I work out the gap between two other dates?: Yes — change both dates. Age from a birth date is just the common case of the difference between two days.