LOCAL dIncDate, aDateRange[1,2], cDateToStick, cMonthPart
SELECT MIN(DATE(val(cYear),val(cMonth),1)) as dmin, ;
       MAX(DATE(val(cYear),val(cMonth),1)) as dMax ;
  FROM InputTable ;
  INTO ARRAY aDateRange  && Save min and max 1st of month in array

SELECT 0
CREATE CURSOR tblPeriods ( cYearMonth C(6), ;
                           cYear C(4), ;
                           cMonth C(2), ;
                           cQuarter C(2) )

dIncDate = aDateRange[1,1]              && Start at first month
DO WHILE dIncDate <= aDateRange[1,2]    && For each month through the last
   cDateToStick = DTOS(dIncDate)        && Convert to YYYYMMDD 
   cMonthPart = SUBST(cDateToStick,5,2) && Snag MM

   INSERT INTO tblPeriods VALUES ( cDateToStick, ;
                                   cDateToStick, ;
                                   cMonthPart, ;
                                   'Q' + TRANSFORM(CEILING(VAL(cMonthPart)/3)) )

   dIncDate = GOMONTH(dIncDate,1)       && next month
ENDDO