Computing Birth From Tombstone Inscription Dates

Many of us have had the puzzling experience of finding an ancestor’s tombstone marker that reads something like this:

Jane Doe, died May 6, 1889, age 71y, 7mos, 9dys

How do we determine her birth date? Shirley A. Scott provides the following formula:

1. With a calculator in hand, enter the date of death in number by year, month, and then day. The example above will read 18890506.
2. Subtract the age of the person found on the tombstone. The age shown in the example should be entered as 710709. You will get an answer of 18179797.
3. Subtract 8870 from 18179797 to correct the months and days. The answer will be 18170927.
4. Translate 18170927 back into year, month, and day. You will have 1817 September 27 (i. e., September 27, 1817) as the date of birth.