JULIA writes -
In the book 1984, it is Winston's job to edit and rewrite all the facts, past, future, and present. So that they all fit the current declarations of the Party. There are many thousands of others doing the same thing. They are sent instructions of exactly what to edit and how, and that's what they do. They work in The Ministry of Truth, which is a giant pyramid shaped building in London.
There are many clues in the book as to exactly what's going on now.