This date of birth calculator estimates age, birthday timing, and date differences from a birth date and a chosen reference date.
Everyday life
Date of Birth Calculator
Calculate age, birthday timing, and date intervals from a birth date.
Calculator
About this calculator
Formula notes
Age and birthday intervals use calendar dates, with separate handling for date-only and time-based inputs.
Worked examples
- Example: someone born on 1990-05-10 is 36 years old on 2026-05-10.
- A person born on 2000-05-10 is 26 years old on 2026-05-10.
How to use it
- Enter the date of birth.
- Set the reference date or time when it is different from today.
- Review the age, next birthday, and interval outputs.
Frequently asked questions
Does it account for leap years?
Yes. The calendar calculations account for leap years and the varying number of days in each month.
Is the result legal proof of age?
No. It is a date calculation and should not replace an official identity document or jurisdiction-specific age rule.
Limits and interpretation
- The result follows calendar arithmetic and may not match a jurisdiction's legal definition of age for a particular purpose.
- Birth-date records, time zones, and leap-day conventions can matter when comparing a date-only result with an official document.