How many months is 20 weeks?

Katie β€’ 20 years old, FTM to baby boy Kaden Chance πŸ’žπŸ‘ΆπŸ»β˜ΊοΈ
I've seen so many different calendars that say 4 months then others saying 5. It's really confusing. Does anyone agree with this chart? Or do you use something else.