Returning Hours A Call Was Open

What I am trying to do is look at a 30 day history of calls that were closed and find (in hours) how long the work orders were open. My major problem is working with dates, the results I'm getting appear to be inaccurate. My Code is as follows:


Code:

SELECT C.Priority, MIN(CONVERT([INT], DATEPART(hh, T1.CalcDate), 120)) AS Minimum, MAX(CONVERT([INT], DATEPART(hh, T1.CalcDate), 120))
AS Maximum
FROM HEAT.dbo.CallLog C, HEAT.dbo.Profile P,
(SELECT CallID, CONVERT(datetime, ClosedDate + ' ' + ClosedTime, 120) - CONVERT(datetime, RecvdDate + ' ' + RecvdTime, 120)
AS CalcDate
FROM HEAT.dbo.CallLog C1
WHERE (CONVERT(datetime, CONVERT([INT], GETDATE(), 120) - 30, 120) >= ClosedDate)) T1
WHERE C.CustID = P.CustID AND C.CallID = T1.CallID AND (C.CallStatus = 'Closed') AND (P.CustType <> 'services') AND (P.PrimarySupportGroupID = 'CTS') AND
(C.Priority IN ('1', 'E1', 'E2')) AND (CONVERT([INT], T1.CalcDate, 1) >= 0)
GROUP BY C.Priority
ORDER BY C.Priority



If anyone could give me any suggestions or help me out I would greatly appreciate it. The results are used to draw a bar chart of the information.

Thank you
Court