15dpo late period

I have a question my period is late and the <a href="https://play.google.com/store/apps/details?id=com.glow.android">glow app</a> pushed my period date back and ovulation date back does that mean i didn’t ovulate the day i did ? I’m confused why my period day is pushed back to the 12-16. Ovulation date was December 26th now it’s says December 30th