Yeah, you do have a great point.. I always forget that. 😂 I'm terrible.
I go by day baby is born because a month or 2 months old. Not all months have 4 weeks in them. If you counted 4 weeks as every month your babies birthday wouldn't be the day they are born.
if it helps. The Drs go by the day baby is born mine was the 23rd so every 23rd is when I count her as another month old