MAR1STCMC (V509) reports the century month code (CMC) for the date of the woman's first marriage or cohabitation.
Century month codes (CMC) are particularly useful checking the consistency of dates, calculating intervals between events, and imputing dates when the information for an event is missing or partially complete.
Century month codes (CMC) are calculated by multiplying by 12 the difference between the year of an event and 1900. The year 1900 was chosen as the reference period because all of the DHS-relevant events occurred during the twentieth or twenty-first centuries. The month of the event is added to the previous result.
CMC = (Year - 1900) * 12 + Month
For example, the CMC for June 2002 is:
CMC = (2002 - 1900) * 12 + 6 = 1230
In other words, 1,230 months have elapsed between January 1900 and June 2002. Starting with CMC figures, one can calculate the month and year using the following formulas:
Year = int( ( CMC - 1 )/12 ) + 1900
[int(x) is the integer part of x]
Month = CMC - ( ( Year - 1900 ) * 12 )
The information above is based on "Online Guide to DHS Statistics" (Rutstein and Rojas, 2006) [URL omitted from DDI.].