Retroactive continuity

Retroactive continuity is the deliberate changing of previously established facts in a work of serial fiction. The change is informally referred to as a "retcon," and producing a retcon is called "retconning". It should not be confused with a "plot hole", where the internal consistency of a particular story is at fault for not explaining changes in conditions that could reasonably happen (e.g. a character using a weapon they were not described as finding).

Examples

Resident Evil 0

Resident Evil 0
Bravo's arrival	RE0 establishes that S.T.A.R.S.' Bravo Team arrived at Raccoon Forest and lost contact with HQ on July 23, RE1 originally established that contact was lost on July 24.

Resident Evil

Resident Evil
to be added

Resident Evil 2

Resident Evil 2
Leon's first day	Original RE2 implies that Leon's first day was on Sept. 29, a party was set up for him in the East Office. This contradicts the game itself, by Sept. 28 there was only 4 people alive inside the station and most of the citizens were zombies, thus making the preparations for his welcoming party seemingly impossible.

Resident Evil 3: Nemesis

Resident Evil 3: Nemesis
Raccoon's populance	Serving as RE2's backstory, the Drama Albums establishes that Raccoon has a population of 20.000 people. This was later changed in RE3, where Raccoon's population was set as 100.000 people.

Resident Evil CODE:Veronica

Resident Evil CODE:Veronica
The date of Raccoon's bombing	Wesker's Report II establishes that the Sterilization Operation took place in October 1st, contradicting RE3 which establishes that the city was bombed on October 2nd.
How much time Claire spend on Rockfort Island	CODE: Veronica X contradicts the original Dreamcast version, in the original Claire was under Umbrella custody for more than a week, in X she just arrived at the Island and shortly after the outbreak started.

Resident Evil Outbreak Series

Resident Evil Outbreak Series
The date of Raccoon's bombing	Outbreak contradicts CODE: Veronica by using October 2nd.

Resident Evil 2 (2019)

Resident Evil 2 (2019)
Police Station	RE:2 establishes that the Raccoon Police Station was established in 1969 following the purchase of an art museum. The Resident Evil Outbreak File #2 file, "Marvin's memo", instead describes the museum being purchased in the late 1980s.

Resident Evil 4 (2023)

Resident Evil 4 (2023)
Wesker and Krauser	RE:4 establishes that Krauser and Wesker have never worked together since Operation Javier.