Hello I recently was sent this method for figuring out birth dates. ***** 8870 formula Using the 8870 formula to ascertain a birth date can be a tremendous help to the genealogists, when checking gravestones or death record dates. If a gravestone or death record shows that person died May 6, 1889 and he was 71 years 7 months and 9 days old, but no date of birth listed, in order to correctly arrive at the birth date one has only to use the 8870 formula to quickly get the date of birth, rather than taking time to count backwards. 18890506 (died May 6, 1889) subtract - 710709 (age 71 years, 7 months, 9 days) 18179797 subtract - 8870 (constant) 18170927 (born September 27, 1817) Hope this helps. Sue