Fertile window

Jill
How long is everybody's fertile window, I have 3 apps on my phone,glow,ovia,and my calendar. Glow and my calendar say my fertile window starts today with my period on the 6. Ovia says it starts the 19 with period on the 6 what one would you trust but all 3 have a 7 day fertile window so when should I trust that ovulation should be the 22 or 23