SSRS 2008 DateTime picker to UNIX/EPOCH field

Im trying to write a report that presents data based on a date range(selected by the person running the report) using SQL Server reporting.
I build the start date and the end date as parameters and as a selectable date/Time data type and create a dataset with the following simple query:
SELECT callclass AS CallType, COUNT(callclass) AS Total
FROM opencall
WHERE (companyname = @name) AND (status <> 17) AND (logdate >= @StartDate) AND (logdate <= @EndDate)
GROUP BY callclass

The problem I have is that the logdate field is stored as an EPOCH/UNIX value and therefore the report does not run. How can I get the date/time picker to convert the selected value into an epoch string and return the correct data for the date range selected? Help muchly appreciated.