glow has my period wrong!😡

Maybe I'm wrong but my friend brought it to my attention that her period still hasn't come and she had it calculated to a different day so I looked at mine as well and I always get my af the second week of the month and glow says my af is due the 7th? Anyone else running into this issue? Well now I can see why you need to check cm,BBC, and cervix position and all that jazz.. I hope I didn't just waist a whole week of trying although it was fun and I'm not rushing.