Groupng time in pivot tables showing difference between start and end date

I have start query dates and end query dates and need to find the resolution time in between. This is for around 2000 incidents and could be more every month.

I have added a column to take away the start date from query date but the format of the time, even when i go in custom and do mm/dd/hh is not coming up correctly.

What I would like to do is create a pivot table and show the time in groups (right click group in pivot table) and show all queries in groups of 10 mins, 20 mins etc.
I then need to create a chart based on the averages.

Could you advise how i could do this?

I really really appreciate your help!!

Thank you very much for replying. Just a quick one. What date needs to go into the value? As there are 2 dates?

Thanks very much :-)

Hi, This works fine in the data sheet but however, when i put this into a pivot table the values are shown as DD/MM/1900?? And not the hours and mins?

Is there a way of changing this format to show the same values in the pivot table?

Kind regardsa and thanks for your help