There's no set age that your child should be out of diapers in the day.
However it's best to try to get your child potty trained starting around age 2 or 3 years old.
Most kids will eventually just decide to stop wearing diapers and go to the toilet.
It's not worth the fight to try and force a child to use the toilet when they really are not ready.
Some kids are ready to potty train and be out of diapers by age 18 months while some may not be ready until age 2 or even 3 years old.
In rare cases a child may not be potty trained until 4 or even 5 years of age which is okay as well.
Diapers are so absorbent now that the child does not feel wet and they are more comfortable in the diaper even when wet or dirty.
I would not start worrying about potty training your kid until they are 5 and still not using the toilet.