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An age on date calculator determines how old a person will be (or was) on any specific date in the past or future. Useful for eligibility checks, milestone planning, and historical research.
Formule
age_years = (target_date - birth_date) / 365.25 (years, months, days calculated separately)
- birth
- Birth date (date) — Date of birth (YYYY-MM-DD)
- target
- Target date (date) — Date to calculate age on (defaults to today)
- age
- Age (years) — Age in complete years, months, and days
Guide étape par étape
- 1Subtract birth year from target year to get base age
- 2Check if birthday has occurred yet in the target year
- 3If birthday not yet reached, subtract 1 from years
- 4Calculate remaining months and days for precision
Exemples résolus
Entrée
Born Jan 1 1990, date Jan 1 2030
Résultat
Exactly 40 years old
Entrée
Born Dec 31 2000, date Jan 1 2025
Résultat
24 years 1 day old
Entrée
Future date check
Résultat
Age at any future milestone
Questions fréquentes
How is age calculated exactly?
From birth date to target date, counting complete years, remaining months, and remaining days. Example: born Jan 15, 2000; age on Jan 20, 2025 = 25 years 0 months 5 days.
What about leap year birthdays (Feb 29)?
People born Feb 29 celebrate on Feb 28 in non-leap years. Age increases on their "adjusted" birthday.
Does time of birth matter?
Calendar age calculations ignore time of day. Only dates matter. Someone turns a year older at midnight on their birthday.
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