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Formula for Calculating Birthdates


If you know a person's age on a particular year, you can use the following formula to determine his or her date of birth:
  • Take the known year and subtract the age
  • Take the resulting year and subtract one year
  • Date of birth will always be one of the two resulting years
  • Consult the LCRI for AACR2 Appendix C7 to determine the correct form for the alternative date
Example 1:  1862 minus 83 = 1779  |  1779 minus 1 = 1778  |  Birthdate = 1778 or 1779

010:  : |a nr 00024598
040:  : |a CtY-BR |b eng |c CtY-BR
100:1 : |a Burgess, William, |d 1778 or 9-1862
670/1:  : |a Two sermons, preached in the parish church of Kirby-Le-Soken, Essex ... 1834: |b t.p. (Rev. William Burgess, B.D., vicar of the parish)
670/2:  : |a Venn, J.A. Alumni Cantabrigienses |b (Burgess, William; d. 29 Apr. 1862, aged 83, Thorpe, England; vicar)

Example 2:  1838 minus 19 = 1819  |  1819 minus 1 = 1818  |  Birthdate = 1818 or 1819

010:  : |a nr 00026243
040:  : |a CtY-BR |b eng |c CtY-BR
100:1 : |a Bittleston, Henry, |d b. 1818 or 19
670/1:  : |a Two letters to an Anglican clergyman of the High Church party: |b t.p. (Henry Bittleston, M.A., of S. John's College, Oxford, late curate of Margaret Chapel)
670/2:  : |a Foster, J. Alumni Oxonienses |b (Bittleston, Henry; matric. 18 Jun. 1838 aged 19)
 

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