Most toddlers are out of diapers during the day by age 3 to 4 years old.
However it's also common for some toddlers to be out of diapers and potty trained during the day by 18 months to 2 years old.
All kids are different and will potty train at different ages.
I would not worry about the kid potty training until the kid gets to 5 years old and above and not potty trained.
There's no age limit for wearing diapers and if the toddlers needs to wear diapers then they should but you should potty train by age 4 before the child goes to Kindergarten.
it's good to let diaper rash air out.
It's also good to let your baby or toddler who is in diapers go diaper free for an hour or two hours per day to allow their skin to breathe.
Wearing diapers prevents the kids skin from breathing and they are wet with urine and poop when they do poop.
The diaper holds most of the urine away from their skin so they don't feel really wet unless the diaper is soaked.
Most kids will spend 3 years in diapers while some kids may be potty trained and out of diapers before 3 years old and some wear diapers until 4 or 5 years old.
The kid is wearing the diaper 24 hours per day 7 days per week which does not allow the skin to breathe.
So it's good to let the diaper area of the kids skin dry out and get some air.
Also wash the baby or toddlers diaper area down even if they pee and make sure they are dry before putting a new diaper on them.
To do diaper free time for your baby or toddler you have to be aware and watch them often in case they pee or poop.
If it's an infant or or baby that is not mobile then you can lay the baby on a towel or sit the baby on the towel when they are sitting upright.
The towel will catch any pee or poop that the baby releases when not in a diaper.
For a toddler that is mobile you have to watch them real closely and if you notice they are going pee or poop or about too take them to the toilet.
That can also be a good way to introduce them to the toilet.
I let my toddlers go diaper free for a few hours per day when I knew they would not pee or poop.
My toddlers when they got to 2 years old would pee and poop on a schedule and they would pee every 2 hours or so.
So I would allow them to go diaper free to air out their skin for a few hours then I would put them back in their diapers before they usually peed.
That way I would not have to worry about them peeing on the floor.
For infants I would lay them on a towel as they would pee at any time or even poop at any time.