In Platinum, after you beat the main story, you can catch Eevees in the trophy garden, but they are extremely rare. It took me 3-4 hours to catch a male and female one. Saved that bad boy twice to make sure, and breed them in my SoulSilver game. Currently, I have 30 Eevees in SoulSilver alone, include all 7 of it's eeveelutions. A couple of the Eevees are foreign. I hatch a new Eevee egg every Sunday afternoon after I beat Sabrina. Riding around Saffron City (cause it's a circuit) a few 1,000 times then the egg hatches, unfortunately, I only have 2 female Eevees of the 30 Eevees. I am an Eevee breeder.