Giratinas pokedex page shows that it learns aura sphere at 37, but mine learned it at lv. 90. I checked both sections (black/white and heartgold/soulsilver), and I'm confused.
In Diamond, Pearl, and Platinum it learns Aura Sphere at 90. At Lv. 37 it only applies to those 4 games listed.
Giratina's Gen IV learn sets