Question: how to evolve eevee into umbreon y?
Answer: First of all, to evolve Eevee into Umbreon in X/Y, you'll have to gain full friendship. After that, you'll have to level up DURING 8PM and 4AM. It should evolve. If you accidentally evolve Eevee into Espeon, then you must've leveled it up during 4AM to 8PM, so make sure you check the time.