Problem Converting CHAR To DATETIME

hello all,

I am having a problem calculating the difference, in days, between two dates, STARTDATE and ENDDATE. The data is stored in the database as char(8), formatted YYYYMMDD. "Null" values are stored as '00000000'. When I try to use DATEDIFF an exception is thrown: "the conversion of a char data type to a datetime data type resulted in an out-of-range datetime value"

How can I fix this, and a get a result even if STARTDATE or ENDDATE is '00000000'? Changing the format of the stored data is not an option.

Thanks for any assistance.

Mike



CREATE TABLE dbo.DATETIME1 (
ID1 int,
STARTDATE char(8),
ENDDATE char(8)
)
INSERT into DATETIME1 (ID1, STARTDATE, ENDDATE)
VALUES (
1, '20070105', '20070108'
)
INSERT into DATETIME1 (ID1, STARTDATE, ENDDATE)
VALUES (
2, '20070105', '00000000'
)
Select * from DATETIME1
Select DATEDIFF(d, STARTDATE, Convert(datetime,ENDDATE) ) as Difference
from DATETIME1
WHERE ID1 = 1