 Although many viewers take it for granted that the comet of the  title is Halleys Comet, this is not specifically stated in the  film. In fact, the comet of the title was the Great Comet of 1811  (formally designated C/1811 F1 by astronomers). Halleys Comet,  which appears only every 75 to 76 years, appeared in 1758 and 1835;  it did not appear in 1811.