After when...

Hi to all moms!

Im a FTM of an 8 month old and I'm so curious about something.

When you say how old is your baby do you say it by months or weeks?

I hear some moms saying stuff like my baby is 40 months or like in weeks when they're just 3 years and I'm like say what? lol

I use to say weeks when my baby was tiny then I just went by months and planing to just say a year once he turns one in a few more months instead of saying months lol

Like when do you stop saying weeks?