Finding time duration between a start date & time with end date & time

Hi all! 

I'm looking for any formula or power query to calculate a total time duration within a day, given the start date, start time, end date, end time. Most of the dates will equal the same but there are some with the end date being the next day. I'd like to be able to exclude any overlaps as well. Currently, I have a large embedded IF formula:

=IF(AND($G4=$O4,$H4<$H5,$P4>=$H5,$P4<$P5,$H4<$H3),$P4-$H4,IF(AND($G4=$O4,$G4>$G3,$H4<$H3,$P4<$P3,$H4<$P3,$P4<$P5),$P4-$H4,IF(AND($G4=$O4,$H4>$H3,$H4>=$P3,$P4>$P3),$P4-$H4,IF(AND($G4=$O4,$H4=$P4),0,IF(AND($G4=$O4,$H4<$P3,$P4<=$P3),0,IF(AND($G4<$O4,$H4<$P3,$P4>$H4),($P4+1)-$P3,IF(AND($G4=$O4,$O4<$G5,$O4<$O5,$H4<$P3,$P4>$P3),$P4-$P3,IF(AND($G4=$O4,$G4>$G3,$H4>$H3,$P4>$P3,$H4>$P3),$P4-$H4,IF(AND($G4=$O4,$G4<$O5,$P4>$P3,$P4>$H5,$H4>$H3,$H4<$H5),0,IF(AND($G4=$O4,$O4=$G5,$H4<$P3,$P4>$H5,$P4>$P3,$P4>$P5,$P2>$P3),$P4-$P2,IF(AND($G4=$O4,$H4<$P3,$P4>$P3,$P4>$P5),$P4-$P3,IF(AND($G4=$O4,$H4<$P3,$P4>$P3,$H4<$H5,$P4<$P5),$P4-$P3,IF(AND($G4=$O4,$H4<$H5,$H4<$P3,$P4>$P3,$P4>$P5),$P4-$P3,IF(AND($G4=$O4,$O4=$G5,$H4<$P3,$P4>$H5,$P4>$P3),$P4-$P2,IF(AND(ISBLANK($O4),ISBLANK($P4)),0,IF(AND($G4<$O4,$H4<$P3,$P4<$H4),($P4+1)-$P3))))))))))))))))

This seems to work for the most part but there are a few that I just can't get. I also pulled up my query and started to enter in the time durations manually and it couldnt come up with anything automatic for me. There must be an easier way for me to do this other than trying to create an IF formula for each answer that turns up incorrect. I have a screen shot below.