How to use this tool
Enter a birth date and an as-of date. Completed years and months use calendar arithmetic: a month-end anniversary is clamped to the final day of a shorter month. The remaining days are counted after the last completed month. Total days use calendar dates at midnight UTC, so daylight saving changes do not add or remove a day.
Try these values
Someone born on May 9, 1994 is 32 years, 5 months and 10 days old on October 19, 2026. For a January 31 birth date, February 28 in a non-leap year counts as one completed calendar month under this tool’s convention.
Choose the right as-of date
For a birthday, an application or a historical record, calculate age on the date that actually matters. Someone who turns eighteen next week is still seventeen today. The as-of field lets you check a past or future date without changing the birth date. This calculator reports calendar age; it does not decide the eligibility rules used by a school, employer, insurer or public authority.
Why the month-end rule matters
Months have different lengths, so a calendar age cannot be found by dividing the number of days by thirty. This tool counts completed months from the starting date, using the final valid day when a month is shorter. That keeps the remainder nonnegative around February and months ending on the 30th or 31st. If an organization uses a different birthday convention, use its stated rule for that purpose.
Common questions
Can I calculate age on a past date?
Yes. Change the as-of date to any date on or after the birth date.
How are leap-day birthdays treated?
Month-end anniversaries use the last valid day of the month. This is a calculation convention; legal age rules can differ.
Is my birth date stored?
The calculation is submitted to this server, but it is not saved to an application database. Do not enter information you do not want processed.
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