CD1 today or tomorrow?

Cortney • Wife. Mom of girls 👧👧👧. 8.5.19 👼. Blessed with our 🌈 coming 6.18.20 🤰👶💙

So I track my ovulation with OPKs, AF just showed up (10:15 PM my time). I've seen different things saying that today would be CD1, but I've also seen where CD1 would be tomorrow, since it showed up so late in the day. I usually start in the mornings. Which day would you consider CD1?