I'm not sure if this Pokemon would be tournament legal, but there's a full chance that it is not hacked.
The date is the only glaring problem here, but there's one such scenario where this is possible. If at the time the Fletchling egg was hatched, the original trainers DS clock showed 1/25/16, then the day it was hatched would also be the same. This means that although it has a wrong date, it's a fully legal Pokemon, seeing that nothing else is wrong here.
As a note, no, releasing a hacked Pokemon is usually harmless to your game as only the method of hacking is damaging and electronically traceable.
Source: Half my Pokemon in XY were caught in 2011 (the game wasn't even released then) because I was experimenting time based events.
Hope I helped!