You can either input that date to a date format, or construct it like a SAS date literal ('01JUL2013'), DDMONYY(YY)
, or construct it as a date value directly.
INTNX is probably your best option here to construct it; you don't need all that work.
%let start_date = %sysfunc(intnx(Quarter,%sysfunc(date()),-4),DATE9.);
%put &start_date;
You can leave DATE9. to use it as a date literal, or remove the ,DATE9.
to get the numeric value that can be used directly. You would use this as "&start_Date."d
to use the date literal.