Date of Birth Finder
Know your age but not your date of birth? Enter your age and an 'as of' date and we will find the day you were born.
Defaults to today
Please enter your age in years.
Frequently Asked Questions
How does the date of birth finder work?
You enter your current age and an 'as of' date. The calculator subtracts the age from that date to find the day you were born. Adding months and days makes the result exact.
Why do I get a range of possible birth dates?
If only the age in years is given, any birth date within the last year could match, because a person is 'X years old' for a whole year. The valid range is shown instead of a single date.
How can I get an exact date of birth?
Enter the extra months and days along with the years. With all three parts, the calculator can pinpoint a single exact date of birth.
What is the 'as of' date?
It is the date at which the given age applies. It defaults to today, but you can change it, for example to a date in the past.
Is the finder accurate for February 29 birthdays?
Yes. The date library accounts for leap years, so a February 29 birthday resolves to the correct date in leap years and a valid adjacent date otherwise.
What if I enter an impossible age?
Ages are validated between 0 and 120 years. Impossible inputs (negative, or more than 30 days / 11 months) are rejected with a friendly message.