HERE it is from a table (Now I used a temporary table BUT ONLY for illustration IN your situation it would be the real table)
/* I used a temporary table BUT ONLY for illustration
the values I used are from your posting Posted Today @ 6:13 AM */
CREATE TABLE #T (D VARCHAR(20))
INSERT INTO #T(D)
VALUES ('01/12/2012'),('03/Dec/2012'),('01/01/13')
SELECT D as 'Input value', CAST(D AS DATE) AS 'Output' FROM #T
Results
Input value Output
01/12/2012 2012-01-12
03/Dec/2012 2012-12-03
01/01/13 2013-01-01
With your new data:
CREATE TABLE #T (D VARCHAR(20))
INSERT INTO #T(D)
VALUES ('01/12/2012'),('03/Dec/2012'),('01/01/13')
INSERT INTO #T(D)
VALUES ('04/01/2013 15:02'),('21/Dec/12 2:17 PM')
SELECT D as 'Input value', CAST(D AS DATETIME) AS 'Output' FROM #T
Results:
Input value Output
01/12/2012 2012-01-12 00:00:00.000
03/Dec/2012 2012-12-03 00:00:00.000
01/01/13 2013-01-01 00:00:00.000
04/01/2013 15:02 2013-04-01 15:02:00.000
21/Dec/12 2:17 PM 2012-12-21 14:17:00.000
I hope this assists you. If NOT please post why not and maybe someone can assist you further.