Proc Expand linear interpolation without calendar adjustment

[dsriggs11]

Is there a way to use proc expand to interpolate a time series from quarterly to monthly frequency without taking the number of days into account?  Treating all quarters/months as if they have the same number of days?

[ghosh]

proc expand data=qtr_series out=mth_series from=qtr to=month;
   convert analysis_var / observed=average;
   id date_var;
run;