The simplest approach would be to convert the character date to a SAS (numeric) date before loading it into SAS VA. That way it will properly identified in your VA data source as a date.
Can use the TreatAs function to convert date to numeric value( which will be stored as the number of days between January 1 1960 and the date).
See how to use one filter for multiple data sources by mapping your data from SAS’ Alexandria McCall.
Find more tutorials on the SAS Users YouTube channel.