This s dumb

So I'm four days late and today actually shld be my last day onAF 
I go to glow and click period late and it then changed my exp AF to next week
Why wld it do that like that is stupid as fuck so I had to switch it back to the first date it gave which is correct .... Smh this is why I don't stress over these apps and just let my body do Wat it was made to do either bleed or birth a child !!!!!!