Question: what time should you evolve eevee into espeon?
Answer: You'll find an Eevee, make that Eevee your buddy Pokemon, and walk that buddy 10km or more. Once you're CERTAIN you've walked that far, you can evolve your Eevee to attain one or the other evolution types. Evolve Eevee at night to get Umbreon, or during the day to get Espeon!