Drools editor in JBDS shows error message if rule include the keyword "today"

Issue

With Drools perspective, error message displays in the Problem window if user write a drl as follows:

rule "GoodBye"
    when
        Message( status == Message.GOODBYE, myMessage : message, today <= "2015/07/26" )
    then
        System.out.println( myMessage );
end

Error message:

Unable to Analyse Expression today <= "2015/07/26":
[Error: Comparison operation requires compatible types. Found class java.util.Date and class java.lang.String]
[Near : {... today <= "2015/07/26" ....}]
                ^

How to fix it