How do you get newmoon island in Pokemon Diamond?

To get to new moon island in Pokemon diamond you have to go to canalave city and go to the house next to the sailor that takes you to iron island and if you see a boy in bed go talk to tha lady next to him and then talk to him and then go to the sailorand he will take you to new moon island,cresselia is there, go talk to it. good luck

also for platinum

new moon is where you get darkrai fullmoon is where cresselia is