Quick question!

Brianna • 🎀Kennedy Marie Peace🎀 2/19/15
Ok this may be a dumb question but, how do you ladies go by months after your baby is born? By the actual date every month or by the day the they were born. For example, my daughter was born Thursday Feb 19. So do I just go by every 19th of every month for her age (because they don't all fall on Thursdays)? Or is it every 4 weeks exactly? Lol sorry I'm not sure how to word it, I'm so confused. Probably overthinking it too.