The Eberron setting would later make this idea a major element, detailing a more complex orrery of 13 outer planes, with Xoriat or Dal Quor filling the role of Nemesis.
Years earlier, the Planescape fansite The Mimir described an Outlands calendar, postulating an annual cycle in which each of the 16 planes that surround the plane of neutrality gets a month of dominance over the Land's weather, almost as if their influence waxed and waned as Eberron's outer planes do.
The Planes of Law boxed set detailed a location known as the Modron Cathedral in the realm of Regulus on the plane of Mechanus. Within is a vast Orrery, a gigantic model of spheres and gears, "constantly spinning and moving about," that function as a working model of the multiverse. There's an illustration of it on the cover of the box:
Apparently this is an accurate model of how the Planescape multiverse works, and it's an orrery.
In Planescape in general, portals often open and close in cycles, their destinations sometimes changing in cyclical patterns. In the world of Greyhawk, the portals of Tovag Baragu shift in accordance to the movement of Greyspace's planets and moons. The Causeway of Fiends opens portals to Hell and the Abyss four times a year, growing large enough to accommodate entire armies once every 80 years or so.
In the adventure Return of the Eight, the witch Iggwilv and the demon Tuerny hope to summon a fiendish army, but the ritual must be performed on Dark Night, "a special night with magical significance for plane-crossing and world-crossing magic," when the "conjunction of Oerth and its moons were favorable for interplanar travel and the creation of new gates." The Blood Moon festival may draw Oerth closer to the lower planes, and Faerieluck may draw it closer to the plane of Faerie.
In Dungeon #23 (published in 1990), an adventure called "The Pyramid of Jenkel" was explicit about the idea of turning, orbiting planes: "In the case of Juncert, time and the movement of the multiverse collaborated in an ecliptic movement of planes to a juncture that opened beneath the city. The Prime Material plane, plane of elemental Fire, and plane of Tarterus focused for an instant on one spot. Two gates opened at once beneath the city. Some parts of Juncert were sucked through to destruction in the plane of Fire; some were transported, almost intact, to the horrors of Tarterus; and some were merely swallowed by the very earth on which they stood."
I've been trying, off and on, to figure out ways to incorporate the rules for orrery cosmologies found in the 3rd edition Manual of the Planes, the Eberron campaign setting, and sources like Malhavoc Press's Beyond Countless Doorways into the Great Wheel cosmology. Because it seems that the Wheel does turn; we just don't have any clear and consistent rules for this.
