Age Difference Calculator
Compare two birth dates in years, months, days and exact total days, and see both people's ages on the same date.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
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Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
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How to use this calculator
Enter both birth dates and a comparison date on or after both births. The report identifies the older person and shows both calendar ages.
Whole calendar months anchor to the earlier date and clamp to a shorter month end. The exact day gap is constant; calendar years and months are not fixed durations.
A worked example
June 15, 1990 and September 20, 1993 are 3 years, 3 months and 5 days apart under this calendar convention.
Will changing the comparison date change the birth-date gap?
No. It changes each person's displayed age, while the exact gap between their birth dates stays the same.
Which calendar and years are supported?
Gregorian input coverage is 1900-2100 unless the method states a narrower range. Results explain calendar conventions and local date boundaries. Astronomy uses a level horizon at sea level. CSV, print and copy retain the result rules; calendar files contain only calculated events. Nothing is scheduled automatically.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.