Update only Date Part : Sql Server

Select *,
dateadd(dd,datediff(dd,SS.StartDateTime,'2012-07-19 00:00:00.000'),SS.StartDateTime)
from t_sessions S
INNER JOIN tIdx_ConferenceSessions CS
ON S.PK_Session = CS.FK_Session
inner join tIdx_SessionSettings SS
on s.PK_Session = SS.FK_Session
Where FK_Conference = 893