convert datetime error

Hi I have a stored procedure that is trying to pass datetime parameters @StartDate and @EndDate but when I run the query I get the following Error....

Arithmetic overflow error converting expression to data type datetime.

Below is my Stored Procedure....

ALTER Procedure [dbo].[Test]  
 @StartDate  datetime, @EndDate  datetime
as 

begin
set nocount on;

-- exec test '01/01/2009','01/01/2020'

SELECT DISTINCT
  F.EpisodeSys ,
   F.ResidentSys ,
  VR.DisplayName ,
  F.OrgEntSys AS FacilityID ,
  VO.FacilityName ,
  VE.AdmissionDate ,
  VE.DischargeDate
  FROM     [D].dbo.FactLoadExceptions AS F
  INNER JOIN [B].dbo.VisionvwResidents AS VR
  ON F.ResidentSys = VR.EntitySys
  INNER JOIN [B].dbo.VisionvwOrganizations AS VO
  ON F.OrgEntSys = VO.OrgEntSys
  INNER JOIN [B].dbo.VisionEpisodes AS VE
  ON F.EpisodeSys = VE.EpisodeSys
  WHERE    CensusDateKey >= @StartDate
  AND CensusDateKey <= @EndDate
  ORDER BY AdmissionDate
end

I should note that The CENSUSDATEKEY field is an INT type I need to convert it to Datetime type