Age Calculator: Exact Age in Years, Months and Days
Exact age, total days lived and the next birthday.
Use via API
Exact age in years, months and days on a given date, with totals in days and weeks and the next birthday. Send JSON, get JSON back.
POST https://pithlab.com/api/v1/tools/age-calculator
curl https://pithlab.com/api/v1/tools/age-calculator \
-H "Authorization: Bearer $PITHLAB_KEY" \
-H "Content-Type: application/json" \
-d '{"birthDate":"1990-05-15","asOf":"2026-10-20"}'About the Age Calculator
Calculate exact age in years, months and days from a date of birth, plus total days and weeks, the weekday you were born and days to your next birthday.
How to use the Age Calculator
- Enter the date of birth.
- Leave the second date as today, or change it to find the age on any other date.
- Read the exact age, the totals in months, weeks and days, and the countdown to the next birthday.
Examples
Input
1990-05-15, 2026-10-19
Output
Age on 2026-10-19: 36 years, 5 months, 4 days (13,306 days)
Input
2000-02-29, 2025-02-28
Output
Age on 2025-02-28: 25 years (9,131 days)
Frequently asked questions
How are the months and days counted?
The calculator counts whole months from the birth date to the target date, then the days left over. When a month is shorter than the birth day, the anniversary falls on its last day: someone born on 31 January turns one month old on 28 or 29 February.
How are leap-day birthdays handled?
Someone born on 29 February is treated as having their birthday on 28 February in common years. Some laws use 1 March instead for legal age, so check the rules that apply to you.
Does my time zone affect the result?
Only in choosing today's date, which comes from your device. The calculation itself uses calendar dates, so it never shifts by a day because of time zones or daylight saving.