how to compare two date in a if statement?

[alepage]

%let File1Date=SEP2020;
%let File2Date=OCT2020;
%LET Nobs1=5;
%LET Nobs2=5;

Data _null_;

if input(&File1Date.,monyy7.) ne input(&File2Date.,monyy7.) then call symputx('Nobs1',0);
run;
%put &Nobs1. &Nobs2. ;

[Kurt_Bremser · Accepted solution]

Without quotes, SEP2020 is a variable name for the data step compiler. You have to enclose the macro variables in double quotes to make them strings.