Bernardo Bertolucci stated that in an interview, he filmed the scenes of the movie based on the four seasons. If you notice, the meeting of the boys is summer, the adult reunion of Alfredo and Olmo takes place in a fall moment. The Fascist takeover is winter, while the end of World War II is spring.
The film's six million dollar budget was supplied by three different sources: two million dollars from United Artists, two million dollars from Paramount Pictures, and two million dollars from 20th Century Fox.
The original uncut version is five hours and seventeen minutes long, and features additional dramatic scenes, actual animal killings, and explicit sex scenes including one involving Alfredo, Olmo, and Neve.
Bernardo Bertolucci once said of this film: "At first we planned it as six episodes for television. But in elaborating the scenario, we began to feel that for political, social, and narrative reasons, it belonged on the large screen."
Bernardo Bertolucci himself cut the three and a half hour version that was originally shown internationally, which he did to appease the studios and financiers, who wanted to use an even shorter cut, that was never released. He still says he prefers the original five hours and seventeen minute cut. His main complaint with the international release, was the English title "1900". With the original title "Novecento", he meant to imply a tale of the twentieth century.
Principal photography started on this picture in July 1974, and was completed nine months later in May 1975, with extra filming continuing right up until September 1975, making the shoot span a period of fourteen months.
Two years earlier, Robert De Niro won an Oscar for playing Vito Corleone, a role that had already won as Oscar for Marlon Brando two years before that. Gérard Depardieu would later be nominated for a Best Actor Oscar, and win a Best Actor award at the Cannes Film Festival, for his performance in Cyrano de Bergerac (1990), a role that had already won an Oscar, forty years earlier, for José Ferrer.