Can you provide more info? What youre asking is straightforward to achieve in ReadyAPI!, so we'll need more info to work out the problem.
You say you cant generate the query parm date values but why not? What is actually happening when you try? What does the logging indicate? What mechanism are you using for the property expansion? Where are you sourcing the date values from? Screenshots?
The more, concise info you provide the quicker someone will be able to respond with the solution.
if this helped answer the post, could you please mark it as 'solved'? Also if you consider whether the title of your post is relevant? Perhaps if the post is solved, it might make sense to update the Subject header field of the post to something more descriptive? This will help people when searching for problems. Ta