Period Approximation Chart

Date Wanted	Known Information	Formula
Birth	Age at dated event	Subtract age from date Add 5 years to each side Search 11 year period
Birth	Marriage date	Subtract 16 years from date Subtract 40 years from date Search period between dates
Birth	Birth or Christening of child: Female - only child	Subtract 16 years from date Subtract 50 years from date Search period between dates
Birth	Female - Several children	Subtract 16 years from date of first child Subtract 50 years from date of last child Search period between dates
Birth	Male - Only child	Subtract 16 years from date Subtract 70 years from date Search period between dates
Birth	Male - Several children	Subtract 16 years from date of first child Subtract 70 years from date of last child Search period between dates
Marriage	Age at dated event	Calculate age 15 Add 25 years to date Search period between dates
Marriage	Birth or Christening of child: Only child	Subtract 34 years from date Add 1 year to date Search period between dates
Marriage	Several children	Subtract 34 years from date of last child Add 1 year to date of first child Search period between dates
Death		Calculate birth date Add 90 years Search period between date last known alive and 90th year