a way to age a tamagotchi is to set it to a minute before its bed time, then when its asleep set it to a minute before it wakes up. keep doing that until you get the desired age. Another way is to fastforward their life by debugging, which i do NOT reccomend, because it can ruin your tamagotchi and it wont be able to work again(but in most cases things work out ok)
hope that helped!