where the data comes from is defined by the DATA= option of the PROC PRINT statement, So you identified my error. (It was not intentional, just wrong).
The print step might work better, defined like[pre] PROC PRINT DATA= DENTAL2_2 ;
where put( FILMDATE, vldYr. ) = '1980' ;
RUN; [/pre]but you still have to create the format VldYr with PROC FORMAT. The on-line doc for PROC FORMAT has relevant "Example 3: Writing a Format for Dates Using a Standard SAS Format" at
http://support.sas.com/documentation/cdl/en/proc/61895/HTML/default/a002473487.htm (of course, your inputs are date-time values rather than date values, so you will be using date-time constants in the VALUE statement ranges == more
good SAS learning
PeterC