Subtracting datetime cells

I am trying to subtract two cells that are in the format yyyy-mm-dd hh:mm:ss AM to create a column "Duration since last event". I have looked at subtracting them and changing the formatting of the answer cell, the datedif() function... everything!


Ideally I would like my results to be like so (where B3= A3-A2) with column B in hh:mm:ss

A B

1997-03-03 4:00:00 PM
1997-03-03 6:00:00 PM 02:00:00
1998-03-03 6:00:00 PM 8760:00:00

Is this possible?
Thanks in advance for any help!

=A3-A2 should work in B3

You need to format B3 as [hh]:mm:ss

you need the square brackets to display hours over 24

Thank you!
My "Calculations" was turned on manual and I forgot - so all the answers were wrong before.