How to modify formula

Hello Guys,

I would need some help.

I have this kind of data with multiply date and time. I try to count the overlays minute by minute.

Right now the format in F6 is Date and TIme, same format as in column B and C, but I'd like to leave the Date and change it to just Time or Text format in order to use the formula  with multiply different dates. How should I modify the formula in F7, so that I can use it with other days too and don't have to change the dates in F6,G6,etc.,  every time? Hope, this make sense.

Thanks for your help

Legendy