In the New Testament baptism has taken over from Old Testament circumcision and is a sign that we belong to God. No definite time period. They must first of all be able to repent and place faith in Christ. One cannot be baptised before salvation. They can of course get sprinkled, wet, soaked, immersed, but it is not Christian baptism.
Christian baptism can only occur after salvation.
It has no real significance to the individual unless they are saved. There is not one Scripture supporting infant baptism. A baby doesn't have the ability to repent and place faith in Christ. When a person can repent and place faith in Christ then they are at an age where baptism is significant. Before this point it is only a ritualistic ceremony.