A working chronology of the Black Mirror episodes, which all share a universe

Season 4 confirmed it: all the events of Black Mirror take place in the same universe, an apparently incredibly environmentally diverse one with a dark and turbulent history.

If we've solved 'where' with regards to the episodes, in a sense, then it begs the question, 'when?'

Intrigued by Screen Crush's very thorough video breakdown of every Easter Egg in seasons 1 - 4 (below), I've attempted to arrange every episode in chronological order.

- Certain episodes we know with certainty take place before or after another, as they either directly reference other events that have happened, or tease them coming in the future.

- Some of the Easter Eggs confirm a shared reality but are no use in terms of chronology, e.g. the same pregnancy test seen in 'Be Right Back' and 'White Christmas'. Others only imply a link between episodes, e.g. Irma Thomas's ballad 'Anyone Who Knows What Love Is (Will Understand)' being used in multiple episodes.

- An episode occurring after, say, three episodes, puts it later in the Black Mirror timeline, but few can be pinned to a definite position with certainty (they have just simply not been Easter Egged in other eps. In these cases, and for the sake of this post holding together, I have employed good old fashioned guesswork based on the evidence and how advanced the technology is, which leads me to the final note:

- This is an absurd exercise. Charlie Brooker and Annabel Jones plan new episodes each season, they didn't have it all figured out right from the pilot, and I doubt they obsess about chronology as I have for some reason chosen to.

Era 1 - all taking place either at the same time or within the same year

Must take place at the same time as 'The National Anthem' (identical headlines seen on UKN news ticker) and 'Fifteen Million Merits' (billboard of Abi seen on a building).

Era 1 - but not necessarily at the exact same time as the above

Era 2

Must be after 'The National Anthem' ('PM Callow to divorce' headline on news website), 'White Bear' ('Victoria Skillane trial latest' on same website), 'Fifteen Million Merits' (social media post about Hotshots reality show), and 'The Waldo moment' (sticker on Kenny's computer of Waldo face).

Must be after 'Fifteen Million Merits' (Abi's porn film Wraith Babes is complete and available on VOD in a hotel).* Additionally, the memory scanning technology feels pretty rudimentary.

Must be after 'The Waldo Moment' (streamer has username 'I_AM_WALDO'), 'White Bear' (White Bear symbol seen on jail cell door) and 'The National Anthem' (PM Michael Callow divorce trailed on news ticker).

Must be after 'The National Anthem' ('PM kicked out of zoo' seen in Lacie's social media feed).

Era 3

Must be after 'White Bear' (Blue says she previously worked on the Iain Rannoch case, and social posts about Skillane later seen), 'The National Anthem' (Michael Callow is a trending topic) and probably after 'Nosedive' (ticker says 'Reputelligent shares nosedive' - the software featured in the episode). Must be before 'Playtest' ('Shau Saito announces immersive new gaming system' reported on news ticker, presumably before things seriously went south with the system in 'Playtest'), 'Men Against Fire' (military AR program only just announced on news ticker) and 'Black Museum' (ticker reveals cookies have only just been given human rights).

Era 4

Must be after 'Hated in the Nation' (see above) and 'White Bear' (VR cards for whack-a-mole game carry White Bear symbol).

Must be after 'Men Against Fire' (fight imagery blocked by monitoring system is from that ep).

Nothing to go on, but the tech is fairly sophisticated and similar to 'ArkAngel's.

No (useful) Easter Eggs, but the android technology feels more advanced than the earlier cookies.

Must be after 'Playtest' (see above).

Futuristic episodes both share the same dating app (a reception in 'USS Callister' is seen using it).

Era 5

Must be after 'White Bear' (Skillane's mugshot exhibited along with shotgun and ski mask), 'White Christmas' ('DOUBLE SUICIDE' referenced on wall and cookie human rights mentioned), 'USS Callister' (cloning machine and lollipop from ep exhibited), 'Playtest' (Cooper's headset exhibited), 'Hated in the Nation' (drone bee exhibited), 'ArkAngel' (broken, bloodied tablet exhibited), 'Crocodile' (bloody bathtub, the site of Mia's penultimate kill, exhibited), 'San Junipero' (reveals tech to "upload old people to the cloud" was developed in St. Juniper's Hospital, 'The National Anthem' ('PM Callow marries pig' ticker). Must be before 'Metalhead', ('autonomous military dog robot unveiled' headline seen in news ticker).

Okay, so that headline above was from a flashback within 'Black Museum', but seriously, how can any of those stories take place while multi-weaponed, killer robot dogs roam a mostly humanless, desolated environment?.

*It's confusing as to how Wraith Babes came to be on VOD and how the environment of 'Fifteen Million Merits' existed. One theory: everyone involved was a cookie, as with 'Hang the DJ'.

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I am almost certainly missing things, if you've spotted any other useful Easter Eggs or have your own theories please let us know!