Why would these change?

The 7th was my first green day, then yesterday I got a positive opk, and it changed it all. Last month it didn't? Last month I also had 5 positive opk during my green days, so I'm irritated that they have moved. It says I ovulated today because of a .4 spike in temp too, last month was almost a full degree change. I haven't even had EWCM yet. Ugh. Why would it change the dates just because I got a positive opk? (It moved it forward like I missed BDing on most of my fertile days.) I don't think I agree with the app this time around.