Formula for Calculating Birthdates

If you know a person's age on a particular year, you can use the following formula to determine their 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

When adding alternative dates to an access point, follow RDA 9.3.1.3 and record both years in full. In the 046, record the years in square brackets separated by a comma, following EDTF standards (detailed instructions are available in DCM Z1 046).

Example 1:  1862 minus 83 = 1779 · 1779 minus 1 = 1778 · Birthdate = 1778 or 1779

010     ‡a nr 00024598
040     ‡a CtY-BR ‡b eng ‡e rda ‡c CtY-BR ‡d DLC
046     ‡f [1778,1779] ‡g 1862 ‡2 edtf
100 1   ‡a Burgess, William, ‡d 1778 or 1779-1862
400 1   ‡w nnea ‡a Burgess, William, ‡d 1778 or 9-1862
670     ‡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     ‡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 ‡e rda ‡c CtY-BR ‡d DLC
046     ‡f [1818,1819] ‡2 edtf
100 1   ‡a Bittleston, Henry, ‡d 1818 or 1819-
400 1   ‡w nnea ‡a Battleston, Henry ‡d b. 1818-19
670     ‡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     ‡a Foster, J. Alumni Oxonienses ‡b (Bittleston, Henry; matric. 18 Jun. 1838 aged 19)

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