The same Shaymin was hack checked
here, and was stated to be a hack; so proceed with caution.
That said, they may have missed something.
There's 2 PIDs with those exact IVs and nature, and only one of them gives Mischievous as a characteristic.
This one also makes the TID perfectly reasonable (frame ~9000).
So I suppose my response would be outwardly legal (although perhaps I've missed something the other person was aware of, such as commonly hacked OT, etc.).
Seems doubtful that it's legitimate. 10000 seems like something someone would enter if typing, and 1/1/2015 is the default for an application which
could do this sort of thing.
No way to be sure though.
If it's the same one as
here, definitely hacked.
OP said:
IVs: The exact IVs of all 6 stats (please do not include ranges). Use an IV Calculator such as
Metalkid's if you need to.
Please find the IVs, these are important in hack checking.
Message to hack checkers:
Please do not post here unless you're pretty confident about your check.
I'm not gonna name names, but we don't need people saying "seems fine" or "matches the details on Serebii/Bulbapedia/etc.". These can (shockingly) also be looked up very quickly by a hacker and give little evidence one way or the other.
Obviously, saying "doesn't match the details on Serebii/Bulbapedia/etc." is perfectly fine to claim it's hacked, assuming you know there are no other events which could result in the Pokémon.