Sorry, here is the data.

--===== If the test table already exists, drop it

IF OBJECT_ID('TempDB..#mytable','U') IS NOT NULL

DROP TABLE #mytable

--------Create test table----------

CREATE TABLE #mytable

(

DateStart DATETIME,

DateEnd DATETIME

)

---------Sample Data-------

Insert into #mytable (DateStart,DateEnd)

Select '2013-06-03 08:00:00.000', '2013-06-05 17:00:00.000' UNION ALL

Select '2013-06-07 14:00:00.000', '2013-06-07 15:00:00.000' UNION ALL

Select '2013-06-08 08:00:00.000', '2013-06-08 09:00:00.000' Union ALL

Select '2013-06-27 08:00:00.000', '2013-06-28 17:00:00.000'

--------What i Tried-----

select * from #mytable

select

Convert(date,DateStart)as DateStart,

SUM(case

when Convert(time,DateEnd) < '12:00' then dateDiff(hh,Convert(time,DateStart), Convert(time,DateEnd))

when Convert(time,DateStart) < '12:00' then dateDiff(hh,Convert(time,DateStart), Convert(time,'12:00'))

else 0

end) as AM,

SUM(case

when Convert(time,DateStart) > '12:00' then dateDiff(hh,Convert(time,DateStart), Convert(time,DateEnd))

When Convert(time,DateEnd) > '12:00' then dateDiff(hh,Convert(time,'12:00'), Convert(time,DateEnd))

else 0

end) as PM

from #myTable group by DateStart

---Problem: Does not take into accout mutiple days--