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In Oz we have no universal method of notching time or assigning arbitrary numbers to year-spans. I'm told that the Quadlings live quite comfortably without any system at all, since the climate there more less precludes seasonal variation. The Gillikinese and the Emerald City refer to the passage of time in terms of the reigns of the various Ozmas or, since the Wizard first arrived, the various reigns of the Throne Ministers. The first, the seventh, the twelfth year of the Emperor Shell's reign, and so an. Here in Munchkinland the length and disposition of our months vary according to cycles of the moon. In years of a jackal moon, for instance, we skip the month of Masque, out of some old superstition no one remem- kers. In years when the sun casts no shadow on Seeding Day, we add seven weeks of agricultural season called the Corn Time, If it rains too much in the spring we just skip over Guestlight. So, our years being irregularly shaped, they don't line up for easy counting. No one tries to do it.
Nipp to Dorothy Gale[src]

This timeline is a work-in-progress, an outline of the history of Oz as told in The Wicked Years by Gregory Maguire.

The Ozma Years

  • The matrilineal House of Ozma is established: A monarchy traditionally ruled by an "Ozma", the hereditary name passed down between mother and daughter.
    • The Ozma line descends from a Gillikinese clan, and through Lurlinist tradition, claims legitimacy through a purported divine relationship with the Fairy Queen Lurline, fabled creator of Oz; as each Ozma is believed to be Lurline reincarnated.
      • Faith in Lurline would considerably run out of fashion in Oz, however, there is still a winter holiday dedicated to her, known as Lurlinemas.
    • Each Ozma is given a unique companion title so the citizens of Oz can distinguish between each Ozma and her predecessors.
      • Depending on the argument, historians recognize between forty and fifty legitimate Ozmas and their regents, including…
    • Ozma Initiata; the first Ozma, said to be the daughter of Lurline.
    • Ozma the Mendacious; a dedicated maunt.
    • Ozma the Warrior; who conquered the Glikkus and commandeered the emeralds for the capital.
    • Ozma the Librarian; she read genealogies.
    • Ozma the Scarcely Beloved; who overtaxed farmers to begin the construction of the Yellow Brick Road.
  • Ozma the Bilious; besides being known for her large size, expired through an accident involving rat poisoning in the risotto. Her consort, Pastorius, would become Ozma Regent during the minority of their daughter: Ozma Tippetarius.
  • During the rule of the Ozma Regent, Pastorius, the hamlet-capital of Nubbly Meadows is renamed as the Emerald City, and is declared the capital of unified Oz.
  • The Great Draught begins.
  • To distract the urban poor from the deprivations of said Great Drought, Pastorius hosts expensive balls in the court proper and bawdy carnivals of patriotic sentiment outside the palace walls.
  • By balloon, outsider Oscar Zoroaster Diggs arrives in the Emerald City.
    • Diggs successfully mounts a Palace coup d'état.
      • Pastorius is murdered and the child Ozma Tippetarius is given to La Mombey, a witch from Gillikin and an adviser to Pastorius. The witch transformed the princess into a kitchen boy she would later call "Tip".
      • Diggs becomes known as the Wizard of Oz.

The Wizardic Years

  • The Emerald City renovation is completed.
  • Construction of the Yellow Brick Road is expanded.
    • This serves as a highway for the armies of the Emerald City and aids in the collection of local taxes from previously independent populations, especially in the Quadling Country and on the eastern flanks of the Great Kells of the Vinkus.
      • Despite its unprofitable swampy soil, Quadling Country is reported to be situated above vast deposits of rubies, and for this reason the Emerald City and other ruling forces of Oz send their armies to clear the area for mining. These campaigns results in the decimation of both the population and the ecosystem of the area.
  • Animal Adverse laws are enacted (The "Animal Courtesy" acts).
  • Social unrest deriving from the Great Draught promotes an atmosphere of scapegoating and hysterical patriotism; especially in Munchkinland.
    • Nessarose Thropp is named the successor of her great-grandfather, Peerless Thropp as Eminent Thropp. Later, on account of her harsh theological measures and for the use of sorcery to control her subjects, Nessarose would become the sole leader of Munchkinland, the Eminence of Munchkinland.
    • The burning of a grange where opposition meetings were taking place, a reported rape of a couple of Munchkinlanders maidens following a cotillion of the Wizard’s army garrisoned near Dragon’s Cupboard, a Massacre at Far Applerue, and the heavy taxation on farms crops had been “the last straw” as far as Nessarose was concerned.
      • At Colwen Grounds, she communicated her revolutionary outrage through a letter directly towards the Wizard and addressed the senior men among the farming communities and kept her religious agenda in check, and there was a unanimous approval for secession. Declaring Munchkinland‘s independence, Nessarose would have the province break away from Loyal Oz, establishing the Free State of Munchkinland.
  • Under the rule of Nessarose Thropp, the Eminent of Munchkinland, the secession of Munchkinland is conducted with a minimum of bloodshed. They would, however, maintain an uneasy trade relationship with Loyal Oz.
  • The arrival of a visitor, Dorothy Gale of Kansas, results in the death of Nessarose, whose harsh, tyrant rule resulted in her subjects to rejoice in her defeat; the death of the "Wicked Witch of the East".
    • Munchkinlanders would then move on to attack the troops of the Emerald City and Loyal Oz, starting a civil war.
  • Elphaba Thropp is vanquished.
    • The so-called "Wicked Witch of the West", one-time agitator, reclusive leader of the Arjikis of the Vinkus, is subdued by Dorothy Gale.
  • The Wizard of Oz abdicates the throne.
    • After almost forty years in power, the Wizard departs Oz via his balloon, never to be seen again.

The Twin Interregnums

  • Lady Glinda Chuffrey, née Upland, is briefly installed as Throne Minister for a 6 month tenure.
    • Dirt Boulevard, the slum of the Emerald City is 'cleaned up' by the authorities.
    • The Animal Adverse laws are revoked, to little effect; Animals remain skeptical of their chances of being reintegrated back into human society in Oz. Many refuse to return to Loyal Oz from Munchkinland, where they have taken refuge.
    • Overall her brief tenure is thought to be a misguided one, as what most she accomplished was establishing libraries and other foundations wherever she planted her jeweled scepter.
  • The Scarecrow replaces Glinda as Throne Minister; some historians hold that the Scarecrow serving as Throne Minister is not the same Scarecrow who befriended Dorothy, though this assertion is based on circumstantial evidence.
    • The Scarecrow, a figure-head of uncertain provenance, is often assumed to have been installed as a Throne Minister front man by Palace apparatchiks and a cabal of bankers sympathetic to Shell Thropp, the youngest of the three Thropp siblings. The Scarecrow proves a weak, ineffectual figurehead, though his elevation allows Shell to avoid having to challenge Glinda for leadership.
    • After a few years serving as Throne Minister, "an unfortunate accident involving a beaker of lighter fluid" brought an end to the Scarecrow; he was replaced as Throne Minister by Shell Thropp.

The Emperor Apostle

  • Shell Thropp, claiming to have experienced "the Awakening", where he heard the voice of the Unnamed God telling him to lead, crowns himself the "Emperor Apostle of Oz"; having done this through a force of formidable piety and a sacred election.
  • In retaliation for a sortie into Loyal Oz by a band of Munchkinlander guerrillas, Shell authorizes the invasion of Munchkinland for the purpose of appropriating Restwater, Oz's biggest lake.
    • Shell claims to be the rightful Eminent Thropp, due to the death of his older sister Nessarose. However, the role of Eminent Thropp would actually fall to his other sister Elphaba's granddaughter, Rain; his great-niece, of whose existence he is unaware.
  • La Mombey Impeccata is instated as the new leader of Munchkinland, chosen to lead the nation in war against Loyal Oz.
    • Bright Lettins is made capital city of the Free State of Munchkinland.
    • Mombey puts Dorothy Gale on trial for the death of Nessarose Thropp, as a distraction for her plan to attack the Emerald City.
    • She forcefully attempts to recruit Animals into the Munchkinland army by casting a spell on the bridges in Bright Lettins, which prevents the Animals from leaving.
  • Shell declares himself Divine - the Unnamed God in the flesh, as he was born out of an unholy, deformed family whole and perfect.
  • Mombey's Munchkinland attacks the Emerald City by dragon fire, leaving the city venerable.
    • With The Emerald City brought to its knees by the dragon attacks, a parley between Emperor Shell and Mombey is called forth in the city. All the other leaders of Oz make an appearance at this summit:
  • Upon the discovery of Tip actually being Ozma Tipperarius furing this parlay, Mombey is incarcerated and Shell willingly abdicates the throne and hands the power to Brrr as Throne Minister until the princess comes of age to rule.
    • Shell later disappears from public eye and travels off to the Great Kells of the Vinkus where he would spend the rest of his life as a hermit.