Depending on the age of the baby or toddler the diapers should be changed every 2 to 3 hours when they are wet.
Some babies only need a diaper change every 2 hours while some older babies or toddlers can go 3 hours or even sometimes 4 hours without a diaper change.
You should check the baby or toddlers diaper for wetness or poop every 1 hour to 2 hours and if they poop the diaper needs changed as soon as you notice it.
If they are just a little wet then they can go another 30 minutes to an hour before they need a diaper change.
Diapers are very absorbent and can hold quite a bit of pee.
You don't have to change the wet diaper every time they pee.
But as long as you're changing the diaper every 2 to 3 hours you're doing good and keeping them clean.
At night the diaper doesn't need changed and they will be just fine.
But during the day they need a diaper change every 2 to 3 hours if they are wet enough.
You should not go any longer than 3 hours between changing diapers unless they are just a little wet or are dry.