Thanks, @mnvwvnm, yet again for the help.
At the moment, I will stick with your brilliant JS solution at it produces a completely accurate calculation.
The DV query is out by a varying number of days in every test I have done, so keeping the JS solution at least means I have reliable data.
I was looking to switch as DV renders in live preview, but JS only works in reading mode.
I am trying to adjust to the new editor, knowing the old one will be deprecated in time. Thing I miss most is being able to see whitespace / invisibles. The old CSS and plugin solutions don’t work at the moment, and I have had no success when trying to create suitable CSS snippets for CM6.
Thanks and best wishes
Angel