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Bungō Stray Dogs Timeline

BSD is probably my favorite manga ever, but the timeline is devilish and slippery as an eel, so the last two times I've reread it I've noted down any dates I could find, and tried to piece together a coherent timeline. This is the result of that.

I’m considering Dead Apple and BEAST canon for this, but I try my best to only rely on them as further support for things already mentioned elsewhere.

If a year has multiple events, I'll be listing the earliest events last . If I don't know when an event happened in a year relatively, I'll put it in brackets.

2000:

I think it's stupid and futile to try and line up BSD with the real world temporally—as in, to try and line up the events with any real world date—because the world is so clearly different from ours that it's not even really applicable. I use 2000 here arbitrarily as the start of the main manga because it's easier and more organized to use dates than to say, like, "when this character was 15". I chose specifically 2000 just because it's an 'easy' year, the millennium.
The start of the main manga must happen sometime between January and October of 2000. There's a discrepancy in Fukuzawa and Ranpo's ages. In Untold Origins, Ranpo is 14, while Fukuzawa is 32 (18 year age difference). Meanwhile, in modern day, Ranpo is 26, while Fukuzawa is 45 (19 year age difference). Since Fukuzawa's birthday is before Ranpo's, the only explanation I could think of for this is that Ranpo was born in 1973, and that his birthday hasn't passed yet in 2000.
Since he's in most of the light novels, I use Dazai's age to date most of them, so for reference: he's 22 in modern day.

1999:

Kyōka likely joined the Port Mafia in 1999, as it's stated in Chapter 49 that she met Akutagawa six months ago.

1998:

It's directly stated that Dazai is 20 in the book.
Also stated in its own and Dark Era's afterwords that the novel takes place two years before modern day.

1997:

[Chapter 43 states that Kyōka's parents were killed, and the ability Demon Snow was passed onto her three years ago.]

[Chapters 74.5 and 75 state that Sigma was born into existence from the Book three years ago.]

1996:

It's mentioned in the afterword that the novel takes place four years before modern day.
Also alluded to various times in the main manga.

1995:
N/A

1994:

Akutagawa joined the mafia, and Dazai became a mafia executive.
Dark Era mentions that Dazai became an executive two years ago. It could be assumed he was promoted after the Colonel died during the Dragon's Head Conflict, freeing up a spot.

Dead Apple states that it happened six years before modern day. Also stated in Fifteen that it happened a year after Fifteen itself.
It's mentioned in Stormbringer that it lasted eighty-eight days.

TBA

The book directly states that Chūya is 16 years old.
Known as the King of Assassins Incident diegetically.

[Chapter 92.5 states that Jōno was recruited to the Hunting Dogs by Fukuchi six years ago.]

1993:

Self-explanatory
Known as The Arahabaki Incident diegetically.

1992:

It's stated in Fifteen that Dazai was 14 when he was an accomplice for Mori's murder

[In Chapter 88, Bram states that he was imprisoned by Fukuchi eight years ago, however I don't exactly trust Bram's perception of time.]

1991:
N/A

1990:
N/A

1989:
N/A

1988:

This was when Mori retrieved Yosano from where she had been staying after the Great War. Mori wanted to take her back to continue his plan of an "Immortal Regiment", and Fukuzawa could not approve of this—thus ends their alliance. The two fought and Yosano joined the newly-formed agency. (per Chapter 66)

After Untold Origins, Fukuzawa sought to found the Armed Detective Agency. Natsume tasked Fukuzawa with guarding Mori, an underground doctor who was looking to assassinate the current mafia boss. Having the two meet was part of Natsume's Tripartite Tactic. (per Chapter 49)

[Chapter 115 states that when she was only a few months old, Teruko used her ability to age herself up in order to work as a partisan. She was nearly killed, and was taken in and recruited to the Hunting Dogs by Fukuchi.]

1987:

Must have happened late 1987, see my explanation up in 2000.
Additionally, Oda is still active as an assassin in Untold Origins. He's 23 in Dark Era, where he mentions he met Natsume & stopped killing at 14.
In Chapter 82, Fukuchi also states that Ranpo and Fukuzawa met thirteen years ago, not twelve.

1986:

Fourteen years ago, Yosano, 11 at the time, was recruited by Mori into the Great War for the use of her ability. She was part of Mori's plan for an "Immortal Regiment", and to prove to the government the usefulness of abilities in warfare. (per chapters 65-66)
Yosano, endlessly beaten down by having to infinitely revive the soldiers, planted bombs and sunk the aircraft carrier they were located on. She was admitted to a mental hospital afterwards. (per Chapter 66)

1985:

Stormbringer and Fifteen both describe the creation of Suribachi City as being at the end of the war. Everything else points at the end of the Great War being vaguely around this time, so 15 years ago is what I've chosen.
The closest thing given to a time-frame for the duration of the Great War is around 10-35 years. In Chapter 39, it's mentioned that the headmaster of Atsushi's orphanage was in his 40s when he died, and his childhood was a time of warfare.
There are a couple of mentions of warfare or the Great War chronologically after 1985. For one, Yosano was on Tokoyami Island fourteen years ago, not fifteen; and secondly, Teruko is mentioned to have worked as a partisan as early as twelve years ago. My explanation is that these were aftershocks or ongoing battles from the Great War—warfare doesn't immediately stop just because it's officially 'ended'.

Fifteen years ago, Arthur Rimbaud and Paul Verlaine, two top-class European spies, were sent to retrieve a high-energy life form being secretly studied by the Japanese government. However, Verlaine ended up betraying Rimbaud, and attempted to kill him. Rimbaud ultimately won, but their fight drew attention. In order to escape, Rimbaud attempted to absorb the life form, Arahabaki, into his ability. He accidentally absorbed the "shell"—a human identity imprinted onto it to keep it in check—, though, and the god Arahabaki was released. A huge crator, which later became Suribachi city, was created by this being. (per Fifteen and Stormbringer)

1984:
N/A

1983:
N/A

1982:
N/A

1981:

Four years before the destruction of Suribachi City, and nineteen years before modern day, an ability user known as Pan created a skill-derived life-form known as Black No. 12, which he controlled using a special metal dust. A French spy was sent to raid Pan and take Black No. 12, whom ended up killing Pan himself. Afterwards, this spy and Black No. 12 became partners and traded birth-names, becoming Arthur Rimbaud and Paul Verlaine respectively. (per Stormbringer)

??:

In Chapter 66, Mori mentions that there was a previous Great War before the one ending in 1985.