Created by schaka on Valkyrie-wow forums.
If you are using the default UnitFrames as shown in the screenshot, it will put timers over your enemy's debuffs and your friends buffs/debuffs, given you are in range when they are applied. You can target and de-target any enemy within range as often as you want and the timers will always be accurate. But please keep in mind, they are static values and not the ACTUAL timers pulled anywhere from the game. They will NOT always show the correct timer.
Newest version should be always available on github: https://github.com/Schaka/EnemyBuffTimersVanilla