Why not use DATEDIFF() ?

>Sir, while using SQLSERVER 2008, I have these codes
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>UPDATE bin1 SET delay_int =
>(select replace(replace(replace(CONVERT(VARCHAR(19), DATE, 120),'-',''),' ',''),':','')as int)
>-(select max(replace(replace(replace(CONVERT(VARCHAR(19), DATE, 120),'-',''),' ',''),':',''))as int
>   FROM bin1 j1
>  WHERE j1.date < bin1.date)
>

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>but is showing this error message
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>and here is table structure
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>Actually I am converting date stamp to INT then subtract.
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>Please help me how to make query workable?