Date of Birth Calculator
Input an age (years, months, days) plus a reference date to recover the likely birth date—perfect for records research or verification.
The date on which the age was recorded (today, document date, etc.).
Example: For “32 years, 5 months, 12 days old on 2025-11-09”, enter 32 / 5 / 12.
Reference date: 11/25/2025
Recorded age: 30 year(s), 0 month(s), 0 day(s)
Estimated date of birth: Saturday, November 25, 1995
Likely date range: 11/26/1994 – 11/25/1995
How to Use This Calculator
Identify your reference date
This could be the date of a census, interview, or today’s date.
Enter full age breakdown
Split the age into years, months, and days (if provided).
Verify the results
Compare the estimated birth date against certificates, registries, or family records.
Formula
Date of Birth = Reference Date − (Years, Months, Days)
Range Start = Reference Date − (Years + 1 year) + 1 day
Example: Age 30y 6m 9d on 2025-11-09 → Birth ≈ 1995-05-31.
Research Tips
- Cross-check multiple documents; reported ages can vary by a year or more.
- Remember that some cultures count age differently (inclusive counting, lunar calendar).
- Use the range to search registries that sort by year or quarter.
- Note the reference date for future researchers—context matters.
Frequently Asked Questions
What if months/days are unknown?
Leave them as zero—your result will be the best approximation based solely on years.
Does the calculator handle leap years?
Yes—actual calendar arithmetic is used, so February 29 adjustments are handled automatically.
Can I use this for legal purposes?
It provides an estimate, but always confirm with official documents before submitting legally.
How precise is the range?
The range covers one full year of possible birth dates based on the provided age. Narrow it with additional evidence when possible.