When does everyone consider their baby another month older?

I'm going from the birth date. Otherwise it's quite far out for us

I think birth date is correct for months and then weeks are different as an example on the 26th November my little one will be 4 months as born the 26th July but this date in weeks is 17weeks and 3 days

Someone did this to me yesterday! She will be 16 weeks on Monday but won’t be 4 months until 29th so over 10 days difference 😂 I count the months on the actual date of her birth

The next month on the day they were born

I go on his birth date for months and then every tuesday (he was born on a tuesday) for weeks, when do we stop saying how many weeks and say months instead 🙈

Actual date because my little boy is almost 21 weeks but doesn't turn 5 months until the 25th

Month older is the date of birth, weeks older is the day of birth, my little one was nearly 18 weeks before he was 4 months