Adult age check
Input: DOB 2000-01-01, as-of 2026-06-07
Output: 26 years, 5 months, 6 days
Calendar-based year/month/day difference with borrow logic.
Age calculator
Set date of birth and as-of date to get exact elapsed years, months, days, and total days.
Age:
Enter both dates to calculate total days.
Formula and algorithm
- Age is calendar difference between birth date and as-of date.
- If day subtraction is negative, borrow days from the previous month.
- If month subtraction is negative, borrow 12 months from years.
Worked examples
Leap-year case
Input: DOB 2012-02-29, as-of 2026-03-01
Output: 14 years, 0 months, 0 days
Leap-day birthdays are handled by real calendar dates.
Same-day check
Input: DOB 2024-10-10, as-of 2024-10-10
Output: 0 years, 0 months, 0 days
If both dates are the same, age is zero.
FAQ
Can I choose a future as-of date?
Yes, as long as it is not before the birth date.
Does this handle leap years?
Yes. Date parsing and month-day calculations use real calendar rules.
Why show total days too?
Total days is useful for streaks, eligibility windows, and precise tracking.
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Updated: June 7, 2026