George Orwell's novel 1984 is a dystopian vision of a totalitarian society in which Big Brother and the Party control every aspect of people's lives. Not only is there no free speech, but every word and gesture are monitored, and even the suspicion of wrong thinking is punished by the Though Police.
The Party's attitude towards the past is summed up as follows:
’Who controls the past,’ ran the Party slogan, ’controls the future: who controls the present controls the past.’
The Ministry of Truth, where the narrator Winston Smith works, is devoted to propaganda, in part controlling the future by controlling the past. The staff at the ministry are tasked with taking past documents and newspapers and editing them to conform to the current truth as the Party sees it. For example, Winston describes how Oceania seems some years to be allied with Eurasia against Eastasia and other years to be allied with Eastasia against Eurasia. Whenever allegiances shift, the staff at the Ministry of Truth go through all past newspapers and change the stories about the war to reflect the current alliance rather than the actual earlier one.
Thus what the Party does with the past is change it to suit their purposes.