The primary setting of Extraordinary! is called the Mainline of Earth-Prime. This world is most similar to our own, with a fundamentally identical world history and geography, save for some alterations to the real world. This mostly amounts to the existence of settlements and small geographic features such as islands which, in the grand scheme of things, are relatively unimportant. Settings where the geography of Earth is so different that it can be clearly seen from outer space are treated as parallel dimensions to Earth-Prime, while divergences within these dimensions are called split timelines.
Chronology
For simplicity, the chronology of Earth-Prime's Mainline is divided into several pages: Known History is general knowledge which can be found in any library, museum, or online by anyone, in contrast to Secret History which is deliberately hidden from the vast majority of living beings. The prehistoric history of Earth is addressed as Earth History, mostly detailing evolutionary and geological events as well as future history. Because the Earth will receive the most attention and detail, the history of the rest of the universe will be detailed on its own page as Universal History, ranging from events taking place as close as Earth's moon to the edge of the existence itself. Finally, small-scale events of birth, death, and coronation or other changes in leadership will be explored as Individual History.