Finding the difference between two times isn't working for me

Hi,
I have a spread with a column of start times and end times and subtracted them to get the duration of the activity. That worked fine with UK date format and my settings as English UK. But now I have data with US date format and subtract just gives an error. I have tried changing my settings to English US, changing the format of the cells but nothing seems to work. I have attached a spreadsheet with a working UK example and a US one that doesn't. If anybody can tell me what I am doing wrong I would greatly appreciate it. Thanks.
Matthew

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I used

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and formatted for h:mm:ss

You're probably going to need some brute force string manipulation with right mid and left.
This will get the date in A7 converted to a real date and time that can be worked with.

=DATE(MID(A7,7,4),LEFT(A7,2),MID(A7,4,2))+RIGHT(A7,8)

Thank you both very much.
Logit - I gave the sum formula a try but it still didn't work for me.
Jonmo1 - Thank you. I used your formula to convert the start date and the end date and then subtracted them as before and I got the difference in time that I wanted.
Matthew

You're welcome.

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Glad you found the solution.

Guess it's the difference between my US English system and your British English system.