As noted here, Titanic held the record for biggest domestic film for for 620 weeks, or 4,343 days, or 11 years, 10 months, and 19 days.
What about previous record holders? Well, given the sparse data, exact dates can't really be given for films prior to the 1980s, although Gone With the Wind has occupied the top perch for longer than any film, from 1939 to the 1960s. Beginning with E.T., however, it is possible to get some exact info. OK, so here it goes:
Between its May 1977 opening and E.T. release in June, 1982, Star Wars: A New Hope had accumulated a total of $307,263,857, making it the biggest film of all time, surpassing Jaws, whose total was at around $260m. As evident from this chart, Star Wars' total did not approach $200m, let alone $300m, until well after 1977, and it's likely that the film did not surpass Jaws until sometime in the middle of 1978, a year after its release.
E.T. opened on June 11th, 1982. Almost exactly two months later, in August, Star Wars was re-released, adding $15,476,285 to its original tally. That brought A New Hope's total to $322,740,142- the benchmark E.T. had to surpass in order to claim the all-time record.
As it happens, while Star Wars was having its re-release, E.T. was experiencing a stunning run at the box office. The film was #1 for most of the summer, and would end up with 16 weekends at #1, more than any other film and one more weekend than Titanic.
E.T. surpassed the $300m mark on Dec. 11th, 1982, 184 days into its run (see here), and surpassed Star Wars' initial total of $307.3m on Dec. 25th, 1982.
On January 14th, 1983, with a total of $322,956,667, E.T. surpassed Star Was to claim the record for biggest domestic release. If we take mid-1978 as the moment at which Star Wars surpassed Jaws, then that means that it held the record for biggest film of all time for roughly 4 1/2 years, or 54 months.
E.T.'s initial total came out to an enormous $359,197,037. The film had two re-releases, one in 1985, and one in 2002 (which we don't have to worry about). The film's 1985 release was hugely successful, adding $40,607,502 to the film's initital gross for a total of $399,804,539. This number, so tantalizingly close to $400m, would be the domestic benchmark for over a decade, until Star Wars' re-release in 1997.
The Star Wars trilogy was re-released in 1997. The re-releases were spectacularly successful; A New Hope added $138,257,865 to its gross, bringing its total just before Titanic's release to $460,998,007, thereby allowing the film to re-claim the all-time title from E.T.
Star Wars surpassed E.T.'s $399.8m, and became the first film to surpass the $400m mark, on February 13th, 1997.
E.T. was the #1 film of all time, therefore, between January 14th, 1983 and February 13th, 1997. It held the record for an astonishing 5,144 days (801 more than Titanic), or almost 735 weeks (115 weeks more than Titanic), or for slightly more than 14 years.
Star Wars' reign as the new, old champ, of course, did not last long. The film was surpassed by Titanic on March 14th, 1998. Star Wars was, therefore, #1 for 394 days, or 56 weeks and 2 days. In combination with its initial run, the film was #1 for around 5 1/2 years, or roughly 67 months.
In summary, therefore:
E.T. January 14th, 1983-February 13th, 1997 (5,144 days)
Star Wars: A New Hope February 13th, 1997-March 14th, 1998 (394 days)
Titanic March 14th, 1998-February 2nd, 2010 (4,343 days)
Avatar February 2nd, 2010-?
