There is already a thread for this, again, but eevee must be traded to Ruby, Sapphire, or Emerald in order to evolve into espeon or umbreon. You must there build a bond with it and frequently check with the woman in verdanturf town, she will tell you how much it likes you. When she says "it adores you, it couldn't possibly love you any more than it does now", eevee will evolve on its next level.
12am-12pm = UMBREON
12pm-12am = ESPEON
The times are confusing, but correct. Good Luck.