USE Master

GO

DECLARE @dt DATETIME

SELECT @dt = '2014/01/27 01:00 PM'

select REPLACE(CONVERT(VARCHAR(10),@dt,111),'/','')+CASE WHEN DATEPART(HH,@dt) >= 6 AND DATEPART(HH,@dt) < 18 THEN '1' ELSE '2' END

SELECT @dt = '2014/01/27 01:00 AM'

select REPLACE(CONVERT(VARCHAR(10),@dt,111),'/','')+CASE WHEN DATEPART(HH,@dt) >= 6 AND DATEPART(HH,@dt) < 18 THEN '1' ELSE '2' END