The Xehanort War: Official Timeline:
6002 BC:
· Atlantis sinks
· The Keyblade War Begins
5995 BC:
· The Keyblade War ends
· Daybreak Town is reduced to a desert wasteland known only as the Keyblade Graveyard
1921:
· Xehanort is born
June 19, 2002:
· Birth by Sleep Begins
June 21, 2002:
· Lilo & Stitch begins
June 23, 2002:
· Kingdom Hearts: Birth by Sleep Ends
June 24, 2002:
· Lilo & Stitch ends
June 23, 2003:
· Radiant Garden is destroyed by a combination of Xehanort's Heartless armies and Maleficent's invasion.
August 10, 2012:
· Kingdom Hearts 1 begins
September 1, 2012:
· Roxas is born
September 7, 2012:
· 358/2 Days begins
September 16, 2012:
· Kingdom Hearts 1 ends
September 24, 2012:
· Chain of Memories begins
October 22, 2012:
· Chain of Memories ends
August 27, 2013:
· Kingdom Hearts 2 begins
December 31, 2013:
· Kingdom Hearts 2 ends
August 5, 2014:
· Sephiroth kills Thanos
September 24, 2014:
· Re: coded begins
September 25, 2014:
· Re: coded ends
January 6, 2015:
· Dream Drop Distance begins
January 7, 2015:
· Dream Drop Distance ends
July 7, 2015:
· Kingdom Hearts III: The Xehanort War Begins
o Sora finds Eraqus' Keyblade on Destiny Islands
July 8, 2015:
o Alice is captured by Xehanort
o Heroes depart Mysterious Tower
o Riku and Mickey enter the Realm of Darkness
o Sora, Donald, and Goofy meet with Aurora
July 9, 2015:
o Aurora is captured by Xehanort
o Maleficent forges a new group of allies
o Aqua and DiZ are rescued from the realm of Darkness
o Sora, Donald, and Goofy leave Enchanted Dominion
o Maleficent and her new allies attack Disney Town
o Lea and Kairi visit Radiant Garden to get support in the fight against Xehanort
o Sora, Donald, and Goofy arrive in Castle of Dreams
o Cinderella is captured by Xehanort
o Maleficent and her allies steal the datascape before leaving Disney Town
o Sora, Donald, and Goofy crash land in Mount Olympus after being knocked off course by the flying Dutchman
o Riku, Kairi, Aqua, and Lea land in Port Royal and meet Jack Sparrow in Tortuga
July 10, 2015:
o Sephiroth dispatched to kill the three heroes
o Cloud lands in Mount Olympus
o Cloud and Sephiroth duel
o Maleficent uses the abandoned Krei Tech portal facility as a lab for her allies
o Hades and Maleficent have their first date
o Sora, Donald, Goofy, and Cloud leave Mount Olympus
July 11, 2015:
o Snow White is captured by Maleficent
o Maleficent's inner circle discusses the Book of Prophecies
o Sora, Donald, and Goofy arrive in Agrabah, and successfully bring Jasmine back to Mysterious Tower, while Aladdin becomes Agrabah's ambassador in the Coalition
o Riku and company arrive at Isla Cruces
o Daybreak Coalition created
o Maleficent's allies establish a base in San Fransokyo
o Braig talks to Kairi about the Unchained
o Riku, Kairi, Lea, and Aqua leave Port Royal
o Braig reflects on his meeting with Kairi in Radiant Garden
July 12, 2015:
o Maleficent's cabal converts the lair of the forty thieves into a treasury
o Maleficent and Hades sleep together
o Sora, Donald, and Goofy arrive in Beast's Castle, and successfully bring Belle back to the Mysterious Tower
o Cassim becomes a spy for the Coalition
o Kairi regains her memories of her time in Radiant Garden
o Riku, Mickey, Kairi, Aqua, and Lea visit Radiant Garden and drop Ansem the Wise off
o Braig merges Space Paranoids and The Grid
o Maleficent deduces that Jiminy's Journal is a Book of Prophecy after Diablo steals it from Disney Castle
o Heroes regroup at Mysterious Tower to plan their next move
o Tron and a few other programs visit the user world
July 13, 2015:
o Maleficent and Hades go on their second date
o Sora, Kairi, Aqua, Donald, and Goofy leave for Castle Oblivion
o Riku and Mickey travel to the Empire of the Sun
o Sora retakes and passes his Mark of Mastery exam.
o Ventus is reawakened from his coma
o Aqua restores the Land of Departure
o Castle Oblivion party learns about the reincarnation cycle
o Braig frees Terra from Xehanort's possession
o Yzma spirited away to San Fransokyo
o Riku and Mickey leave the Empire of the Sun
July 14, 2015:
o Castle Oblivion party splits up
o Sora, Kairi, Donald, and Goofy visit Radiant Garden
o Aqua, Ventus, and Lea arrive in Arendelle
o Kairi and Sora enter the 100 Acre Wood
July 15, 2015:
o Riku and Mickey visit the Land of Dragons
o Lea helps Elsa practice with her powers
o Ven, Anna, and Kritoff meet Olaf
July 16, 2015:
o Sora, Donald, Goofy, and Kairi arrive in Atlantica
o Hans attacks Elsa's ice castle
o Sora, Donald, Goofy, and Kairi leave Atlantica
July 17, 2015:
o Riku and Mickey leave the Land of Dragons
o Hans is dragged back to the World That Never Was
o Aqua, Ventus, and Lea swing by the Keyblade Graveyard to pick up Terra's armor
o Riku and Mickey pick up Kairi to bring back to Mysterious Tower, but are to diverted to search for one of Maleficent's spies
o Sora, Donald, and Goofy land in Oakey Oaks
July 18, 2015:
o Riku, Mickey, and Kairi land in Monstropolis
o Aqua, Ventus, and Lea arrive in The New World
o Riku, Mickey, and Kairi leave Monstropolis
o Terra and Ludor are exposed, and are forced to flee the World That Never Was, with Sephiroth hot on their heels.
o Sora, Donald, and Goofy leave Oakey Oaks
o Maleficent brings Waternoose and Randall to San Fransokyo to help provide scare power for the lab.
o Terra and Ludor arrive on Maveth and meet Will and Simmons
o Sora, Donald, and Goofy board the RLS Legacy bound for Treasure Planet
July 19, 2015:
o Riku, Mickey, and Kairi travel to the Pride Lands
o Aqua, Ventus, Lea, Cloud, and Tifa leave The New World
o Mulan and Coalition delegates arrive in DunBroch
o Aqua, Ventus, and Lea visit Radiant Garden
o Lea and Ienzo go into Game Central Station
o Sephiroth murders Will as Terra, Ludor, and Simmons flee to Earth
o Riku, Mickey, and Kairi leave the Pride Lands and arrive in The Lost Empire, joining the expedition to Atlantis
o Beck, Paige, Zed, and Mara spend more time in the user world
July 20, 2015:
o Lea and Ienzo leave Game Central Station
o The RLS Legacy brings Sora, Donald, and Goofy back to Radiant Garden
o Aqua, Ventus, and Lea leave Radiant Garden
o Aqua, Ventus, and Lea visit La Cite Des Cloches
July 21, 2015:
o Sora, Donald, and Goofy leave Radiant Garden and arrive in Kingdom of Corona
o Aqua, Ventus, and Lea leave La Cite Des Cloches and make a pit stop in Radiant Garden
o Terra and Ludor arrive on Jotunheim
July 22, 2015:
o Aqua, Ventus, and Lea return to Mysterious Tower to report on their progress to Master Yen Sid
o Terra and Ludor flee Jotunheim after a twenty-four hour battle with Sephiroth, and arrive in Dunbroch. Witch turns them into her personal guard dogs.
July 23, 2015:
o Sora, Donald, and Goofy leave Kingdom of Corona
o Sora, Donald, and Goofy arrive in DunBroch
o Aqua, Ventus, and Lea arrive in The Jungle
July 24, 2015:
o Cassim and Coalition intelligence operatives locate Maleficent's source of income.
o Sora, Donald, and Goofy leave DunBroch
o Braig travels to The Lost Empire
o Sora, Donald, and Goofy arrive in Sherwood Forest
July 25, 2015:
o Riku and Kairi welcomed into the city of Atlantis
o Aqua, Ventus, and Lea leave the Jungle
o Terra and Ludor arrive in Pride Lands Pride Lands at Goofy's suggestion to level the playing field against Sephiroth
July 26, 2015:
o Coalition Raid on Agrabah
o Sora, Donald, and Goofy leave Sherwood Forest
o Aqua, Ventus, and Lea follow Terra and Ludor to Pride Lands to help them fight Sephiroth.
o Sora, Donald, and Goofy arrive in San Fransokyo
July 27, 2015:
o Riku and Kairi leave The Lost Empire
o Terra and Ludor flee Pride Lands only to wind up in Cable Town, where Maleficent captures them.
o Aqua, Ventus, and Lea leave Pride Lands
July 28, 2015:
o Sora, Donald, and Goofy leave San Fransokyo
o Everyone reconvenes back at the Mysterious Tower where they receive Maleficent's demands
July 29, 2015:
o All parties arrive in Cable Town, where the first day of the negotiations begin.
o Braig breaks into the Mysterious Tower, kills Yen Sid, and captures Jasmine and Belle
o Battle of Daybreak Town occurs
o Cloud finally kills Sephiroth.
o Kairi is captured by the Organization
o Maleficent is seemingly killed in the battle and her allies scatter.
o Terra and Ludor are dragged back to the World That Never Was.
o Kairi and the other Princesses of Heart combine their powers to form the Key to Return Hearts, which is then sent to Sora.
July 30, 2015:
o Heroes make a beeline for Twilight Town to use the link between it and the World That Never Was to cross through to attack the Organization
o Sora goes into the virtual Twilight Town and uses the Key to Return Hearts to restore, Namine, Roxas, and Xion
July 31, 2015:
o The heroes press on to the World That Never Was
o Heroes fight their way through to the Round Room
o Sora manages to use the Key to Return Hearts to free both Terra and Ratcliffe before the Key is damaged, sending Kairi's heart back to her body.
o Vanitas awakens and attempts to possess Sora
o Xehanort and most of Organization XIII withdraw to the Keyblade Graveyard, while the Guardians of Light follow
o Kairi, Riku, Donald, and Goofy stay to help Sora break free of Vanitas
o The Final Battle occurs, and Xehanort is finally killed
o Sora seals Kingdom Hearts beginning the process of putting the shattered pieces of the original world back together.
August 1, 2015:
o Member worlds of the Daybreak Coalition celebrate Xehanort's death.
o Lea gives Isa private funeral
o Sora returns to Destiny Islands to recover from the battle.
June 1, 2016:
o Sora, Riku, and Kairi graduate from high school.
The information regarding when the ending of Kingdom Hearts 1 and the events of Chain of Memories occur in relation to 358/2 Days comes from translations of the 358/2 Days Ultimania. The dates as far as when all the games take place in the year are my own speculation and head-canons based on conjecture on how long each world in the main games would take.
Edit: Birth By Sleep's dates are based around the beginning of Lilo & Stitch, which occurs on the date the movie was released IRL. The characters from Lilo & Stitch and its sequels won't be showing up till later in the sequels, but I included them anyway to give some context to when Birth By Sleep happens.