Error in datetime setting

If try this in SQL server error occurs at line 9

DECLARE @patient_id     bigint,@exam_date      datetime,@exam_seq       smallint,@save_datetime  datetime,@edit_datetime  datetime
SET @patient_id=1
SET @exam_date='08/26/2014'
SET @exam_seq=1SET @save_datetime'08/26/2014 09:15:20'===>Error!
SET @edit_datetime'08/26/2014 09:20:12'

How could I fix this error.