Age Calculator

Exact age in years, months and days plus the next-birthday countdown. Free, runs entirely in your browser — no signup, and nothing you paste in is uploaded.

Calendar arithmetic is not subtraction with a divisor. Months are 28 to 31 days long and years are 365 or 366, so "two months and three days" depends entirely on which two months, and any calculation that divides a day count by 30.44 will be wrong by a day or two in ways that look arbitrary.

The correct method counts down units instead: whole years first, then whole months from the anniversary, then the remaining days. It is why an exact age has to be computed against a specific pair of dates rather than derived from a single elapsed duration.

The edge case everything is tested against is 29 February. A birthday that exists roughly once every four years has no universally agreed non-leap-year equivalent — different jurisdictions and different systems land on 28 February or 1 March — so any age calculation has to make a choice there and be consistent about it.