In Terminator 3: Rise of the Machines, Skynet becomes self-aware in 2004.
The film revises the franchise’s earlier timetable. In the original story, Skynet’s activation and the resulting nuclear exchange were associated with 1997, but Terminator 3 depicts efforts by John Connor and others delaying that outcome rather than preventing it.
The 2004 date is part of the movie’s altered chronology and helps explain why the characters believe they have postponed Judgment Day. The film ultimately presents the catastrophe as unavoidable within its timeline, even though its exact date has changed.
This date should not be confused with the 2003 release year of Terminator 3 or with August 29, 1997, the Judgment Day date commonly associated with the earlier continuity. Different films in the franchise use altered timelines, so dates depend on the specific story.