I hack my legendaries in with my trust Action Replay Max. Only the ones like Lugia, Jirachi, Ho-oh and friends who can't be obtained other than going to a Nintendo Event and paying a ridiculous amount of money for them, and you get them at level five (according to.....reliable sources).
Anyway, that's what I would advice. I got my Action Replay from Amazon. And I got it cheap too.
Also, you cannot go to the moon and Jirachi is not there, just to inform you before any idiots start flooding fake explanations in here.
Jirachi info: Grows slow. Base 100 in all stats, like Mew, but a lot better. Also not classed as an uber due to its poor movepool. But still a very good pok�mon. CAN be traded if hacked in. try to get a Modest or Timid nature on it if you are considering using it in your main team.
I'm finished here...
Special thanks to Yossy666 for the avatar and signature images.