Prior to the Great Turf Wars (12,000 years ago)
- Around 12,000 years ago - Judd is born.
- Around 12,000 years ago - A printer used to determine each Splatfest's theme was produced.
- 12,000 years ago - A human is buried with gaming devices. (Sunken Scroll at Stage 26)
- 12,000 years ago - Judd is preserved in a capsule. (Sunken Scroll at Stage 27)
- 12,000 years ago - Flooding sea levels drown out much of Earth's land, its humans, and its flora and fauna. (Sunken Scroll at Page 25)
- 12,000-2,000 years ago - For 10,000 years, there was no activity of sentient life.
Mollusk Era (2,000 years ago)
- 2,000 years ago - Global water levels recede, forcing many marine creatures on what used to be Earth's dry land to evolve and develop sentience. Some of these creatures also develop a humanoid structure. For example, squids evolve into Inklings, while octopi evolve into Octarians and Octolings. The Mollusk Era begins. (Sunken Scrolls at Stages 5, 9, and 10)
- 2,000 years ago - The Inklings begin to use Zapfish as a prized power source. (Sunken Scroll at Stage 1)
- 2,000 years ago - Judd is released from his capsule, and becomes the judge of the earliest known Turf Wars. (Sunken Scroll at Stage 4)
The Great Turf War and surrounding events (100 years ago and after)
- Before 100 years ago - Inkopolis and Calamari County are founded. Calamari County's customary chorus is composed to celebrate and respect the bounty of the sea.
- Around 100 years ago - Cap'n Cuttlefish and DJ Octavio are born. They later become the respective leaders of the Inklings and the Octarians. (Sunken Scroll at Stage 16)
- 100 years ago - Sea levels rise again, forcing the Inklings and Octarians to fight over the remaining dry land. Around that time, the Octarians build the Great Octoweapons. (Sunken Scroll at Stage 16)
- 99 years ago - Cap'n Cuttlefish forms the Squidbeak Splatoon with three other members (possibly including someone who appears to be Sheldon's grandfather, Ammoses Shellendorf) as its leader. (Sunken Scroll at Stage 15)
- After 99 years ago - Ammoses Shellendorf creates five (or eight) blueprints for weapons, including one for the Hero Shot Replica.
- After 99 years ago - The Octarians were victorious through the course of the Great War, aided by their Great Octoweapons. However, a plug being pulled off deactivated their weaponry, allowing their Inkling enemies to prevail and defeat them. The Octarians were later forced into hiding into Octo Valley, where they built and lived in underground domes. (Sunken Scrolls at Stages 13 and 14)
- After 99 years ago - The Turf Wars become a popular competitive sport instead of a serious conflict, as they used to be 2,000 years ago.
Splatoon (present day)
- ? - DJ Octavio begins his career as a disk jockey.
- ? - The Octarians' underground domes show signs of collapsing, and begin to lose power. (Sunken Scroll at Stage 6)
- ? - Agent 3, Agent 4 and Agent 8 are born.
- ? - Marie and Callie are born in Calamari County.
- ? - Inkopolis hosts its first annual Youth Folk-Singing Contest. Marie and Callie win the contest, and their career and fame as singers begin. (Sunken Scroll at Stage 17)
- ? - Annie, Moe, Crusty Sean, Jelonzo, and Sheldon begin operating their shops at Booyah Base. Spyke also works at a back-alley in Inkopolis Plaza.
- ? - Hightide Era, Squid Squad, and The Chirpy Chips perform their popular music.
- ? - After moving to Inkopolis, Marie and Callie also begin their career as announcers for Splatfests and other events in Inkopolis News, as the "Squid Sisters".
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- The Octarians steal the Great Zapfish and other Zapfish from Inkopolis to power their homes and the Great Octoweapons, and prepare for war against Inkopolis.
- Agent 3 enters Inkopolis, and joins Cap'n Cuttlefish's new Squidbeak Splatoon with Marie and Callie (who are Agents 1 and 2), as undercover agents who attempt to rescue Zapfish from the Octarians' control.
- Agent 3 launches several attacks on Octo Valley to save the Zapfish, and destroy the Great Octoweapons in the process. They also acquire Ammoses Shellendorf's plans afterwards.
- Cap'n Cuttlefish is abducted and brought to DJ Octavio's lair.
- Agent 3 fights and defeats DJ Octavio. With the Squid Sisters' help, they bring the Great Zapfish and Cap'n Cuttlefish back to Inkopolis, restoring its power supply. Cap'n Cuttlefish stores DJ Octavio into a snow globe.
Spoilers end here.
(Spoilers for Splatoon 2 below)
Unknown / Before Splatoon 2
- Grizzco Industries is founded and managed by Mr. Grizz.
- The Salmonids migrate to the irradiated waters outside Inkopolis as they undergo their Salmon Run for every 70 years. They also prepare to attack Inkopolis.
- Marina defects from the Octarian army to become a citizen of Inkopolis, and with her friend Pearl they start their own group, Off The Hook. She also becomes a fan of the Squid Sisters.
- Flow, Bisk, and Jelfonzo begin operating their shops at Inkopolis Galleria, where Sheldon joins them as he relocates his Ammo Knights shop there.
Squid Sisters Stories / Prologue
- Marie wins the final Splatfest that she and her sister hosted. No Splatfests occur for a while until the arrival of the new band Off The Hook.
- Inkopolis Square becomes the new hub for Turf Wars, and Inkopolis News' studio has relocated to one of its buildings.
- Callie and Marie spend more time apart, in variety shows and music shows respectively.
- Marie goes to Calamari County to visit her parents, and returns back to Inkopolis. She then searches for Callie.
- Marie goes to Octo Valley, and finds that Cap'n Cuttlefish's shack has been abandoned, and the snow globe containing DJ Octavio has been broken. DJ Octavio later gathers the defeated Octarians, and establishes their new base at Octo Canyon.
- The Great Zapfish is stolen again, plunging Inkopolis' residents into unease.
- Marie goes to Inkopolis Square to seek a recruit to investigate the Octarians, and find Callie.
- With the Squid Sisters being absent, Off The Hook enters to take their places as musicians and hosts for Inkopolis News. They also host the first Splatfests since the Squid Sisters' absence.
- A certain Inkling follows Marie to Octo Canyon, where she appoints them as "Agent 4". Together with Sheldon, the three recover young Zapfish from the resurgent Octarians.
- Agent 4 and Marie stumble into Callie at DJ Octavio's stage, where they find that she has been brainwashed under DJ Octavio's control. After freeing her from her brainwashing, she and Callie reunite and perform their music, helping Agent 4 defeat DJ Octavio.
- The Great Zapfish is placed once again within Inkopolis.
- The current Salmon Runs take place to gather Golden Eggs for Grizzco Industries.
- A young Octoling, Agent 8, finds themselves in an abandoned subway, and is used in several experiments before they participate in the Turf Wars of Inkopolis with other Octolings.
- These events occur before the a little after the Splatoon 2 single player
- Evidence is that the Squid Sisters are together
- Marie says "Callie if you get brainwashed again i'm not helping you!"
- The Squid Sisters also perform Spicy Calamari Inkantaion