"Peter's birthday is coming up next month," I told the neighbor girl. "Peter, tell her how old you are going to be."
"Five," he says with full confidence.
"Five? No! You're going to be three. You're two now, but you will be three next month."
"I two now, I be free on my birfday."
The neighbor girl asks, "Peter, can you count? How do you count?"
Peter holds up one finger, then two, then three, then four...
I encourage him, "Count out loud, Petey. One..."
Peter says, "One...two...five!"
And that explains it.