4. Date of birth and age
(a) What is (N's) [the respondent's] date of birth?
(b) What was (N's) [the respondent's] age at last birthday?
1.5. Age
Age is the interval of time between the date of birth and the date of the census expressed in completed years. When age is not known, estimates should be made based on references to major national events such as hurricanes, civil unrest etc.