Question: how to evolve eevee to umbreon in crystal?
Answer: Level up Eevee at during the day (Espeon) or during the night (Umbreon) once you think its Friendship is at 220. Once you think that your Eevee is above 220 Friendship, level it up in the day time to get Espeon, or level it up at night to get Umbreon. You can level up Eevee through battle or by using a Rare Candy.