215) On what day, month, and year was (NAME) born? PROBE: When is his/her birthday?
KIDDOBCDC (B18) reports the century day code for the child's date of birth.
Century day codes (CDC) are particularly useful for checking the consistency of dates, calculating intervals between events, and imputing dates when the information for an event is missing or partially complete. Century day codes are conceptually similar to century month codes (CMC), but century day codes provide additional detail.
According to the DHS Program's "Calculating the Age of Children More Precisely" documentation,
The century day code is analogous to the century month code and gives the number of days since the beginning of 1900. The century day code for a date of birth is computed in a similar manner to the century month code, using the reported day, month and year of birth, and the reported age in years for living children, as well as an imputation process for incompletely or inconsistently reported information. Note that for simplicity in the calculation of the century day code the assumption is that 1900 is a leap year, but this is also how Excel works too. This doesn't affect any calculations of age as all calculations are using a consistent base.
Age in years is then calculated by subtracting the century day code for the date of birth from the century day code for the date of interview, and dividing the result by 365.25 (allowing for a leap year every 4 years) and taking the integer part of the result to get completed years. For age in months, divide the difference between the date of interview CDC and the date of birth CDC by 30.4375 (365.25 divided by 12 months), and then take the integer part to get completed months.
For more information about the calculation of century month codes, see INTDATECMC (V008).
The century day codes reported in KIDDOBCDC are calculated using the Gregorian calendar.