How many levels does it take to evolve Eevee into Umbreon?

To evolve Eevee into Umbreon you need to make it really happy and level it up at night and it could potentially evolve at any level in order for it to evolve into Umbreon except for Level 10. Ways to make it really happy include having it in your team a lot or feeding it nutrient stuff like Protein, calcium, etc. Night time in-game time varies depending on the Pokemon game however for HeartGold and SoulSilver night time is between 8 PM and 4 AM additionally walking with it, making sure it doesn't faint, feeding it berries that it likes are also ways to raise its happiness.