Replace time part with custom time

I have a scenario where I have to match the system time, but I have to match the current time with a pre-set saved datetime variable in sql server.

DECLARE @SyncDate AS DATETIME
DECLARE @SystemDate AS DATETIME
SELECT  @SyncDate = dbo.TimeTable.auto_time    
FROM    dbo.TimeTable
'1900-01-01 03:00
SELECT  @SystemDate = GETDATE()

I have to replace the @SyncDate with current date and already saved time, i.e:

2015-11-16 03:00

Any body can help?