Zilean stores time as Experience and can grant it to his allies. When he has enough Experience to finish an ally's level up, he can right-click them to impart it. Zilean receives as much Experience as he gives.
Time Bomb
Tosses a bomb to target area that sticks to units that come near it (prioritizes Champions). It detonates after 3 seconds, dealing area of effect damage. If a Time Bomb is detonated early by another Time Bomb, it also stuns enemies.
Rewind
Zilean can prepare himself for future confrontations, reducing the cooldowns of his other basic abilities.
Time Warp
Zilean bends time around any unit, decreasing an enemy's Move Speed or increasing an ally's Move Speed for a short time.
Chronoshift
Zilean places a protective time rune on an allied champion, teleporting the champion back in time if they take lethal damage.