so is my baby not considered 1 month until a month exactly on the date he was born ?

Tamara • Mommy to my 2 beautiful baby boys, Nathan Louis💙 born August 12, 2017 and Parker Joseph May 6, 2019❤️ My whole world😍

he was born August 12th.. 4 weeks old today. but is he not considered a month until September 12?