Why will my tamagotchi not age?

You have to keep it for a certain amount of time (eg. 2/3 week) Then if you feed it, take it to the loo, play with it, give it medicine if needed, give it sleep it will age well. it doesn't all happen in 2/3 days a lifecycle of a tamagotchi is 3 weeks if looked after well and attended to once a day...