Calendar month data points are challenging to reference in the QDM, partly because they are not categorized independently. Constants representing the calendar months “JANUARY”, “FEBRUARY”, “MARCH”, “APRIL”, “MAY”, “JUNE”, “JULY”, “AUGUST”, “SEPTEMBER”, “OCTOBER”, “NOVEMBER”, and “DECEMBER” are required to allow expression of the measures that are concerned with when a specific event occurred during the year. The current QDM accomplishes this by fixing the measurement period for a single year and then specifying the number of days that the logic covers. This has the side effect of limiting the date ranges being evaluated to a single year and prohibiting logic that determines if an event has ever happened within a given set of months. A measure must instead ask if the event happened during this given year. The below example illustrates the issue by showing how to represent events that occurred after “MARCH”:

AND: “Encounter X” >= 3 month(s)starts after start of “Measurement Period”

The 3 months in the example is accounting for January, February, and March. Note that this is only capturing events for the provided year of the measurement period. Adding the months as constants allows us to avoid this pitfall, and more concisely express the measure logic as:

AND: “Encounter X” starts after start of MARCH during “Measurement Period”

With a calendar month constant, a measure can now represent arbitrary time ranges over any measurement period, regardless of start date. It is also clearer that a measure focuses on the actual calendar month, as opposed to an offset of months.