Alternate Access: Plane of Time(Normal):
In order to get keyed for the Plane of Time without having elementals complete, you need to be raided in to Phase 3. Named spawns in Phase 3 have a chance of dropping a Time Phased Quintessence, an alternate Plane of Time key. The list of mobs at the left is by no means complete.
You can loot this, and next time you zone in to Time, you'll be keyed.