When do you catch Dialga and Palkia after the elite four in Pokemon Platinum?

Dialga: After defeating the Elite Four and the Champion, talk to Cynthia's grandmother in Celestic Town. After speaking to her, go to Mt. Coronet and find the Adamant Orb. After you find the Orb, go to the Summit of Mt. Coronet and the Spear Pillar. When you arrive, a blue portal will be there. Interact with it, and Dialga will appear at Level 70.

Palkia: After defeating the Elite Four and the Champion, talk to Cynthia's grandmother in Celestic Town. After speaking to her, go to Mt. Coronet and find the Lustrous Orb. After you find the Orb, go to the Summit of Mt. Coronet and the Spear Pillar. When you arrive, a pink portal will be there. Interact with it, and Palkia will appear at Level 70.