Adventure Time Continuity: After assuming it had ended, 'Distant Lands' gave us more of Finn and Jake, providing closure to their story.
Fiona and Cake Series: Acts as a sequel, adding additional details to the lore of Adventure Time's past.
Reference: Extensive Adventure Time chronology by JM on chronology-d.com (non-canonical comic events not included).
Chronological Structure: The Great Mushroom War continues to be used as year zero (BMW, Bomb of the Great Mushroom War).
More Than 13.7 Billion Years BMW
Primordial Monsters: Existed before time and matter, reality was an amalgamation of conscious monsters like Orgalorg and The Lich.
Lich Entity: A dark consciousness waiting for its chance to extinguish all life in the universe.
Time Room: A dimension inhabited by Prismo, outside of time.
3.7 Billion Years BMW
Catalyst Comets and Elements: Development of death and magic concepts; elementals emerged: fire, ice, candy, and slime.
65 Million Years BMW
Green Comet and the Creation of the Crown: 'Urgence Evergreen,' the ice elemental, creates the magical crown to stop a comet; the dinosaur assistant Gunther uses it erroneously, and the comet destroys Earth.
7 Million Years BMW
Magic City and Vampires: Magic users draw power from the primordial monster called coki; reduces magical power on Earth.
Vampires Before Humans: Hunson Abadeer takes the nusphere, prefers blood for its taste.
10,000 to 1,000 Years BMW
Martian Society and Orgalorg: Green society on Mars governed by Abraham Lincoln faces the chaos entity Golb.
Exile of Orgalorg to Earth: Trapped in the form of a penguin, Gunther.
Around 2,000 BMW
Wars Between Dogs and Rainicorns: In the Crystal dimension, two armies fight for territory, influencing both cultures.
Around 20 BMW
Founding of MOCo: MOS Mastro creates intelligent robots, including Beemo.
5 BMW
Discovery of the Enchiridion and Birth of Marceline: Simon Petrikov, an archaeologist, finds Evergreen's crown and causes his transformation into the Ice King; Hunson Abadeer has a daughter, Marceline.
Year 0: The Great Mushroom War
Nuclear Disaster Brings Magic Back: Destroys much of humanity, releases the Lich.
Blue Catalyst Comet (ZAMW): A new agent of change arrives, eventually to become Finn the Human.
2-5 AMW
Simon and Marceline Find Simon Petrov: They traverse the post-apocalyptic landscape, forming a bond.
13 AMW
Eradication of Vampires and the Founding of Founders Island: Marceline hunts vampires, humans escape to Founders Island.
149 AMW
Revitalization of Magic: Earth's geography changes, creating the U continent.
172 AMW
Birth of Bonnibel and Nettie Bubblegum: Two beings emerge from Mother Gum, creating the Candy Kingdom.
186 AMW
Rise and Fall of Uncle Gumbald: Bonnibel repels his control attempts.
500-700 AMW
Candy Kingdom Expansion Era: Creation of new guardians and candy citizens.
798 AMW
Magic Man Exiled to Earth: Causes chaos on Mars and is stripped of power, sent to Earth.
999 AMW
Formation of Finn's Sword and Prismo's Reincarnation: Through complicated events.
1000 AMW
Reappearance of Orgalorg and the Purple Comet: Orgalorg resurfaces, seeking to absorb power.
1001 AMW
Great Gum War: Conflict between Gumbald and the Candy Kingdom.
Jake Becomes Death: Finn and Jake fight against New Death, influenced by the Lich.
Future
BMO and Future Tales: BMO tells stories from Kgor Mountain.
Humans Return to U Around 13 AMW: Humans return from Founders Islands.