Birth From Death Date Calculator
Genealogists, historians, and legal teams can quickly determine a birth date from recorded age-at-death information.
If the obituary lists an age like “82 years, 5 months, 12 days”, enter each component accordingly.
Recorded death: 11/25/2025, 11:49:00 AM
Age at death: 80 year(s), 0 month(s), 0 day(s)
Estimated birth date: Sunday, November 25, 1945
How to Use This Calculator
Enter exact death date
Use death certificates or obituaries for accurate timestamps.
Record the stated age
Split years, months, and days into separate fields—even if zeros.
Verify the result
Compare the computed birth date with historical documents or family records.
Formula
Birth Date = Death Date − (Years, Months, Days)
Handle month/day rollovers using calendar arithmetic (month-end adjustments)
Time of death reduces the birth timestamp equally
Example: Died 1988-04-10 at 09:00, age 82y 5m 12d → Birth ~ 1905-10-29 at 09:00.
Research Tips
- Always cross-check with multiple documents for accuracy.
- Be mindful of “aged about” phrasing—adjust years or months accordingly.
- Use this estimate to search census records or immigration manifests.
- Note that older records may round ages to the nearest year.
Frequently Asked Questions
What if only the age in years is known?
Leave months and days as 0. The calculator still subtracts whole years.
How precise is the result?
It matches the provided age components. Historical ages may have rounding errors; verify with other sources.
Does it handle leap years and month lengths?
Yes, subtraction respects calendar variations, including February and month-end adjustments.
Can I add weeks or hours?
Convert extra information into months/days before entry, or adjust the output manually after calculation.