Birth and Death Date Calculators

Calculating Dates
Having exact birth and death dates for our ancestors helps us confirm our finds, as well as better identify them in other records. However, finding precise dates can be much more difficult as we research further back in time. We may only have our ancestor’s age (sometimes in the format of years/months/days) at time of death. Or, we may wish to know how old an ancestor would be from their birth date. Using a date calculator can help us with the addition and subtraction necessary to discover our a more precise date. The date calculators listed above can help you determine that information.

A genealogy Date Calculator needs to work the way genealogical records work - which is almost always by first subtracting the years, then subtracting the months, then subtracting the weeks, then subtracting the days.

NOTE: some date calculators use the reverse order, which will calculate a different date in many scenarios!

Records that may give an exact age at death and a death date can be found on:

Tips for Using Date Calculators

 * Be aware that some of these Websites have other types of calculators with different functions, explanations and tips, with various kinds of information. So check out the rest of the page. (The following examples are what you might find for tips)
 * Some calculators may require you to put a 0 in a box instead of leaving a box blank, also using a 0 in front of a single digit month may or may not be required.
 * Due to possible errors or different methodology used in Calculated dates from original calculations. (found on the tombstone, obituary or death certificates), please make a note in your records that the date was calculated..
 * The calculator could also be used to calculate birth year from census data or birth date from wedding date and age.
 * When calculating Dates using the Julian or Gregorian Calendar you can't use the two together.
 * There is what is called a 30-day-month/or **8870 method which assumes that all months have 30 days, many of the headstones and obituary ages at death appear to have been computed using this method. It's an approximation which agrees with the exact calendar month method about 2/3 of the time.)
 * Because of the change from the Julian to the Gregorian Calendar, the calculator may not work for anyone born between Sept. 2, 1752 and Sept. 14, 1752 or when days were lost at the calendar changeover.
 * Be aware the calendar was changed from Julian to Gregorian in which ever country for which you are performing the calculation. See the change from Julian to Gregorian calendar Dates by country.

How to calculate by hand - Estimated date
There is what is called a 30-day-month/or **8870 method which assumes that all months have 30 days, many of the headstones and obituary ages at death appear to have been computed using this method. It's an approximation which agrees with the exact calendar month method about 2/3 of the time.

When the online calculator is not available, use the **8870 formula or the 30 day month length

For example: If a person died May 6, 1889 at age 71 years, 7 months and 9 days:

18890506 Year, day, month of death (yyyymmdd) 1889--05--06 -710709 Subtract age at death (yymmdd) 71yr-07mo-09dd _________   18179797    -Subtract constant 8870 ________ 18170927 Born 27 Sept. 1817 (yyyymmdd) 1817yr-09mo-27dd

This person was born on September 27, 1817