Why does the graph count the tracking as the day it finished on and not the night it was recording?

Hi, I’d really like some help.
My app (on an android device) is telling telling me on the graphs page after tracking as the day it finished on and I was wondering if there was any way I could change it so it states the night it was recording?
For example it will tell me 6/18 Tuesday even though it was recording from 6/17 Monday.
I’ve tried having the set up as “Sleep Day Cut Off” 12.00 and it made no difference to having the set up as 24.00
Any help would be hugely appreciated.
Thanks, Megg.