Here's around how long it takes each stage.
Baby- 1 hour
Kid (a.k.a. Toddler)- 1 day
Teenager- 2 or 3 days (have not counted)
Adult- 4 or so days (have not counted)
Senior- Neverending but you must take really good care
Pausing Tamagotchi slows down the growing process. I only pause my Tamagotchi for school and dance exams. Because mine is a lot of work. I cannot pause my Tamagotchi just by pushing ( A ) and ( B ) just like the rest of you. No. I have Connexion version 1 (don't like version 2s) and I have to go to the clock screen and hold ( A ) and ( C ). Perhaps only pause when absolutely necessary...
