'Black Mirror' Season 4 confirms a long-running fan theory

Spoiler alert! This post contains spoilers for all of Black Mirror, up to and including Season 4. 

With the Season 4 finale "Black Museum," Black Mirror finally confirmed what fans had long suspected: That every episode of the anthology series takes place within a single universe.

The question now is how all these episodes fit together. Does the reality-show dystopia of Fifteen Million Merits come before or after the social media hellscape of Nosedive? What was invented first, the grains from Entire History of You or the cookies from White Christmas?