I need to make baby entity age up but I have no idea what to do?

under the “When entity spawns” procedure, create a wait [x] ticks then on server-side do command where x is the number of ticks you want to wait before the entity grows.

then within that wait block, de-spawn the baby entity and spawn an adult entity. 

So it would look like this

Trigger: When Entity Spawns
wait [4800] ticks then on server-side
do:
    Despawn [baby_entity]
    Spawn [adult_entiry]

I wouldn't recommend using wait procedures but instead using an nbt timer. Since it's a far better method

The problem with this solution is this not the same entity, for example if we rename the baby entity with a name tag, when he will be adult he will lose his name because it's not the same entity, someone have a solution ?