Age calculator — exact years, months and days
Exact age in years, months and days — plus total days and weeks lived, the weekday you were born on, and how long until the next birthday.
Runs entirely in your browser — nothing is uploaded.
Defaults to today.
Month arithmetic clamps rather than rolling over, so 31 January plus one month is 28 February. A 29 February birthday therefore falls on 28 February in non-leap years — the convention most date libraries and jurisdictions use.
How to use
- Enter the date of birth. Any date up to today.
- Optionally change the second date. It defaults to today, but you can work out an age at any past or future date.
- Read the breakdown. Calendar age, total days and weeks, and the next birthday with its weekday.
Questions
How is age calculated exactly?
By counting whole elapsed months from the birth date, then the remaining days from that anniversary. This is more accurate than dividing total days by 365.25, which drifts by a day or more over a lifetime.
What happens with a 29 February birthday?
The anniversary falls on 28 February in non-leap years. Month arithmetic clamps to the end of the month rather than rolling into March, which is the convention date libraries and most jurisdictions use.
Why is 31 January to 28 February exactly one month?
Because adding one month to 31 January clamps to 28 February — there is no 31st. The reverse calculation has to agree, so the gap reads as one month and zero days.
Does it account for time zones?
Dates are handled in UTC, so a daylight-saving change can never shift the result by a day. For a birth date that is exactly what you want.