Age Difference Calculator
Calculate the age difference between two birth dates in years, months and days. Your dates stay in this browser.
How to calculate the age difference
Enter both birth dates, then select Calculate age difference. Either order works. We start at the earlier date, count complete months anchored to its original day number, and then count the remaining calendar days. Supported years are 0001–9999.
Examples
- 1990-05-15 and 1993-08-20: 3 years, 3 months, 5 days.
- 2020-02-29 and 2021-02-28: 1 year, 0 months, 0 days.
- 2024-01-31 and 2024-03-30: 0 years, 1 month, 30 days.
Questions about age differences
Why is there no as-of date?
This result is the fixed calendar interval between two birth dates. Today's date does not change that interval.
Does swapping the dates change the result?
No. The calculator sorts valid dates before calculating. Equal dates give zero years, zero months and zero days.
Why not subtract two whole-number ages?
Whole-number ages omit months and days. Subtracting them can give a different answer, depending on whose birthday has passed.
How are leap days and month ends handled?
A missing day is clamped to the target month's last day. Each complete month is anchored to the original earlier date, so January 31 to February 29, 2024 is one month; January 31 to March 30 is one month and 30 days. These are this tool's calendar rules, not a legal or medical age determination.