Oma's Day



"Oma's Day! The day of judgment marking the end of the Kamen Rider era. Is it the end of history or just the beginning? Choose our future!"

- Opening narration

Oma's Day (オーマの日) is an anticipated event serving as one of the central plot points in Kamen Rider Zi-O, which is set to occur sometime in 2019 according to Tsukuyomi and Geiz Myoukouin. It is later revealed that Oma's Day will occur when Regulus, the brightest star in the Leo constellation, shines at its brightest point, as noted by both Black Woz and Time Jacker Swartz.

However, due to the present day Zi-O temporarily giving up his Ziku-Driver, the expected progression of events that lead to Oma's Day now differ across two divergent timelines. The Time Jackers themselves are trying to prevent both timelines from happening by creating an Another Rider powerful enough to stop both Zi-O and Geiz and have it become king instead.

Possible Timelines
Because of the multiple alterations to the timeline caused by several variables from the future, Zi-O II and Geiz are now destined to do battle on Oma's Day, as revealed to Sougo within his prophetic dreams. The outcome of the battle will decide which of the two timelines become reality, though such a battle did not take place in the original timeline before Geiz and Tsukuyomi arrived in 2018.

Oma Zi-O's timeline
"Sometime in the future, an event known as Oma's Day happens. On that day, you became Oma Zi-O and all the Riders aside from you disappear."

- Geiz explaining Oma's Day to Sougo According to Black Woz, on this day, Sougo used the Zi-O II Ridewatch to make his grand transformation into the overlord Oma Zi-O and destroyed the world using Dai Mazines, eventually wiping out all the Kamen Riders and at least 50% of the Earth's population. This global catastrophe created the dystopian timeline where the Resistance attempts to fight back against Oma Zi-O to no avail, causing Geiz Myoukouin, Tsukuyomi, and the Time Jackers to go travel back in time in an effort to change their future, however Woz followed them through in an effort to stop them, although later enters a feud against his white counterpart in an attempt to secure their own futures.

Geiz Revive's timeline
"On the upcoming Oma's Day, you will destroy Oma Zi-O, and become the one to change history!"

- White Woz revealing the newly diverged Oma's Day to Geiz and Sougo On this day, Geiz defeated Oma Zi-O and became known as the world's savior, later evolving into Geiz Revive. Sometime after this day, the Woz of this timeline traveled back to January of 2019 to assist Geiz and ensure the timeline runs the way he wants, eventually entering a feud with his black counterpart to secure their timelines. Due to this, new Kamen Riders are able to rise, such as Shinobi in 2022 and Quiz in 2040. White Woz describes this timeline to be "at peace, like time itself has stopped".