Yesterday, I placed a Zygarde on the GTS, and I asked in return for a Ho-oh. To my surprise today, I got the Ho-oh, it was shiny, and it had 5ivs! (all in the good places!)
I checked to see the Ho-oh's summary, and it said
Travelled from time and Space from Johto to get to Kalos
What does this mean? is my Ho-oh (gulp) ..not legit?
Random Number Generator
and refers to methods used to trick/abuse the limited predictability of the games' random number generation system in order to generate Pokémon with specific stats and characteristics. To my knowledge, the Gen 6 RNG has not yet been figured out and there is little incentive to do so because the breeding system has become so easy that it's arguably as easy to breed a perfect shiny normally as it is to RNG it. The legendaries have also been made easier to reset for good stats (they have at least 3 IVs at 31), and there are very few in the first place.