DHS Century Month Codes

The Century-Month Code system provides an easy way of working with data coded by month and year, and is the primary way in which dates are coded in Demographic and Health Surveys. A good description is available in the Guide to DHS Statistics (Rutstein and Rojas 2003). The CMC reduces all months to a code taking the value of 1 in January 1900, 2 in February 1900, 13 in January 1901 etc. The conversion of a month and year to a CMC is done by means of the relation:

$\text{CMC}(\text{month,year})=12(\text{year}-1900)+\text{month}$

Likewise, to reverse the process,

$\text{Year = 1900+ int}\left(\frac{\text{CMC}-1}{12}\right)$

and

$\text{Month = CMC}-12(\text{Year}-1900)$

The CMC for February 2011, then would be 12*(2011 - 1900) + 2 = 1333, while the year associated with a CMC of 1267 would be given by year = 1900 + int(1266/12) = 2005, and the month would be July (7), i.e. July 2005.

References

Rutstein, Shea and Guillermo Rojas. 2006. Guide to DHS Statistics. Calverton, MD: ORC Macro. https://www.dhsprogram.com/pubs/pdf/DHSG1/Guide_to_DHS_Statistics_29Oct2012_DHSG1.pdf