"Parameters are not dynamic" to get the latest date in ur viz u have to replace the Existing date in parameter. so the report get refresh with latest date.If you want to refresh data dynamically make sure to use filters instead of Parameter.
I am agree with Sravan. Still i would like to know that, Which version are you using?
As, 10.3 having this feature to select latest date presented in table. Refer the below link for more information about the version.