Date of Birth Calculator
Calculate birth date from age with precision using years, months, days or total days
Calculate Date of Birth
Results
Understanding Birth Date Calculation
How Birth Date Calculation Works
Years/Months/Days Method
- • Subtract days from reference date
- • "Borrow" 30.4 days if needed
- • Subtract months (borrow 12 if needed)
- • Subtract years from adjusted date
- • Results may vary by 1-2 days
Total Days Method
- • Multiply total days by 24 hours
- • Convert to milliseconds
- • Subtract from reference date
- • More precise calculation
- • Accounts for leap years
Common Applications
Medical Records
Estimating birth dates for medical documentation and patient records.
Legal Documentation
Age verification for legal and administrative purposes.
Historical Research
Genealogical research and historical date estimation.
Frequently Asked Questions
How accurate is the birth date calculation?
The calculation provides an estimation that may differ by 1-2 days from the actual birth date due to varying month lengths and leap years. The total days method is more precise.
Why do I need to "borrow" days and months?
When subtracting age from a date, if the days or months result in negative numbers, we "borrow" from the next larger unit (30.4 days from months, 12 months from years) to perform the calculation.
What if I only know my age in total days?
Use the "Total Days" method for more accurate calculations. Simply enter the total number of days you've lived, and the calculator will subtract this from the reference date.
Can I use this for legal documentation?
This calculator provides estimates for reference purposes. For legal documentation, always verify with official birth certificates or consult with legal professionals.
Quick Examples
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