When do you go to the reverse world in Pokemon platinum?

i was going to ask the same question i think its neer the end of the game.

-The first time? When you get Giritina? Or when you go back to get the Griseous Orb?

The First Time/ To get Giritina

The first time you go to the Distortion[Reverse] World, will be at Spear Pillar, the top of Mt. Coronet. Giritina will be Level 47, but you also have to beat Cyrus, his Pokemon around level 45 - 50.

To get the Griseous Orb, after you beat the Pokemon League, a path on Route 214 will open up called, Spring Path. You will need Rock Climb and possibly Surf. It will be the same cave that is in Peal and Diamond where you found/ find Giritina. But where Giritina was in Diamond and Pearl, will be the entrance to the Distortion[Reverse] World.

Hope it helps.

-CelestialIllusion