Optional date prompt not returning any data

[actcognosuser]

Hello ,

There is an optional date prompt in the report when start date is defaulted to Jan 01, 2000 and end date is current calendar day.

The optional filter is defined as
[Reportdate]>=to_char(?StartDate?,'Mon DD, YYYY')
and
[ReportDate]<=to_char(?P_EndDate?,'Mon DD, YYYY')

When the dates are selected on execution it returns right results.
But when nothing is selected in the prompt (defaults have a valid date range), it doesn't return any data.

I included paramdisplayvalue(?StartDate?) and enddate on the report to see what dates it is pulling. It is the right date yet not returning any results.

Please advise.