Slightly complex conversion and date calculation

Every week I receive an output from our database with every case we've handled the previous week, and our results wether we managed to hit the turn-around-time or not on each of them.

The layout is as follows:

CreateTime                StartTime	            SDStarttime	        TATStopTime	      TATTargetTime
Thu 2008-01-03 13:46	Thu 2008-01-03 13:46	Thu 2008-01-03 14:03	01.03.2008 14:03:50	01.03.2008 17:00:00

The output is a bit weird, because three of the date columns are in the format
"wed 2008-4-14 13:05:55", while two of them are in a proper date format, ie "14.04.2008 13:05:55". Now, the two that already are in a proper format can be changed using the format cell method.
The other three cannot. No matter what format I try it will not read it as a date. =Datevalue does not recognize it.

The only way I've managed to extract the date is to use the Text-to-column conversion.

Now, the first bit:
Is there any other way I can convert the three first columns automatically to a date value?

The second bit is regarding calculation of TAT.

The TAT is calculated based on the type of case. The target time is then given in the last column. If the TAT Stop Time is passed the Target Time, the system markes the case as missed.

So far so good.
However, I want to calculate average handling time for the cases, and therefore need to calculate the difference between the Start Time, and the TAT Stop Time, and I would like to have the output in number of days, hours, minutes and seconds. Depending on what function i use I either manage to get the days or networkdays, or I get the hours, minutes, etc. How do I get them together?

I've attached a sample output of the columns in question in the file sample.xls