Formula
The count walks from the date of birth to the date you choose, borrowing a month when the day has not been reached:
Age = calendar years, months, and days from birth to the chosen date
The date-difference page counts only the days between two dates. This page keeps the years and months.
Assumptions
- Both values are calendar dates.
- The age date is on or after the birthday.
Worked example
Someone born on March 15, 1994 is 32 years, 6 months, 29 days old on October 14, 2026.
Input definitions
- Date of birth
- The first calendar date.
- Age on this date
- The date the age is measured on. It can be today or any later or earlier date after the birthday.
Limitations
Time of day and time zones are ignored. A birthday later today is already counted as that calendar date.
Questions
Why not just count the days?
A day count is the date-difference calculator. An age keeps whole years and months.
What if the dates are the same?
The age is 0 days.