Century Day Code (CDC)
In DHS‐7, the DHS program introduced a new concept the Century Day Code (CDC). The CDC is
analogous to the century month code and gives the number of days since the beginning of 1900. The CDC for
a date of birth is computed in a similar manner to the CMC, using the reported day, month and year of birth.
Note that for simplicity in the calculation of the CDC the assumption is that 1900 is a leap year, but this is
also how Excel handles it. This does not affect any calculations of age, as all calculations are using a
consistent base.
The formulae to calculate the CDC of a date is an iterative process calculated in 2 steps:
Step 1: calculating the number of days since 1900 to the yyyy-1.
The formula to calculate the CDC is not as straight forward as the formulae to calculate the CMC
because the number of months per year is a fixed number (12 months). In the case of the CDC, the
calculation process for step 1 must be done with an iterative function because the number of days per
year varies depending if it's a leap year (366 days) or if it's regular year (365 days).

Date = [dd]/[mm]/[yyyy]
CumulativeDays1 = 0
do i = 1900 while i < [yyyy]
CumulativeDays1 = CumulativeDays1 + 365 + (LeapYear = false);
enddo;

Note: the statement (LeapYear = false) will return value of 0 or 1
Step 2: calculating the number of days from yyyy to mm/dd
An interactive function should be used in this process because the number of days per months also
varies. There are months with 30 and 31 days, besides February can have 28 or 29 days depending if
it's a leap year or not.

Date = [dd]/[mm]/[yyyy]
CumulativeDays2 = 0
xdays = 0 (working variable)
do i = 1 while i < [mm]
if mm in 1,3,5 xdays = 31 endif; (January, March, May)
if mm in 2 xdays = 28 + (LeapYear = false) endif; (February)
If mm in 4,6 xdays = 30 endif; ( April, June)
CumulativeDays2 = CumulativeDays2 + xdays;
enddo;

Note: the statement (LeapYear = false) will return value of 0 or 1
CDC = CumulativeDays1 + CumulativeDays2 + [dd]