for,mula for b day

8870 Formula for Determining Birthdates:

Use this formula when the tombstone lists no date of birth, but does list the date that a person died - say May 6, 1889 and was 71 yr, 7mo, 9 days old. In order to arrive at the birthdate, one has only to use the 8870 formula to quickly get the date of birth rather than taking time to count backward.

The 8870 formula using the above date and age as an example:

• Date of death - 1889 May 6 = 18890506 (where 1889=year, 05=month, 06=day)
• Age at death - 71 yrs 7 mo 9 days = 710709 (where 71=years, 07=months, 09=days)
• Subtract 710709 from 18890506 =18179797
• Subtract the Constant (8870) from 18179797
• Result = 18170927 (where 1817 = year, 09 = month, 27 = day. This person was born 27 Sep 1817)

If the age in months and age in days are less than the month and day in the date of death, you can just subtract directly, i.e.,

• Date of death - 1868 Dec 25
• Age at death - 45 yrs. 5 mo 4 days
• Subtract 45 from 1868 = 1823
• Subtract 5 from 12 = 7
• Subtract 4 from 25 = 21
• Result = 1823 Jul 21 or the date of birth