I would like the day and night evolution to be altered.
Day, Night, and Morning
Umbreon - 8PM - 4AM (8 hours) Night
Espeon - 4AM - 8PM (16 hours) Day/Morning
Slyveon should be morning. That is from when the moon is still up in the early morning, until the sun rises.
It should be something like this, 8 hours each:
Espeon 10AM - 6PM
Umbreon 6PM - 2AM
Slyveon 2AM - 10PM