Reverse Birth Date Calculator
If you know a person's age on a specific date and want to know when that person was born, this calculator will use that information to reverse calculate the person's birth date. For example, older headstones show death date and age at death, which can be used to calculate birth date using reverse date math.
Don't know exact age or date? Use our Reverse Age Calculator, which provides a date range of when the person was likely born.
Entry Fields
In the Age field, enter the exact age of the person for whom you are calculating. Use the next field to indicate when the person was this age. Enter the person's exact age, using the years, months, and days entry fields. For instance, if you enter 35 years, it's assumed the person is exactly 35 years old on the age on date you enter; If you enter 24 years, 20 days, it indicates it's 20 days after the person's 24th birthday.
In the Age on Date field, enter the date on which the person was the age you specified.
Optionally, enter the name of the person for whom you are calculating.
About Calculator
If you know a person's exact age on a specific date, this calculator will use that information to reverse calculate the person's birthdate. The birthdate should be accurate provided that age and age on date are correct, and the age on date is based on the Gregorian Calendar and subtracting out the age does not cross-over, backwards in time, into the Julian Calendar.
One area where this calculator is helpful is when reviewing headstones where only the age at death and the date of death are known. With that information, this calculator will indicate the birth date. However, keep in mind that it is only as accurate as the information source; that is, if the age and date at death are correctly reflected on the grave marker.
There are many instances where reverse calculating birthdate is helpful. As long as you know the age on a given event date, you can determine the birthdate; Or, depending on your application, the start date.
This calculator generates a specific birthdate. Therefore, if either age or age on date (or both) are approximate, you may find the Reverse Age Calculator more helpful, since it generates the likely range for birthdate.