The idea of a trip around the world within a set period had clear external origins and was popular before Verne published his book in 1873. Even the title Around the World in Eighty Days is not original. Several sources have been hypothesized as the origins of the story.
The most obvious took place between 1869 and 1871, when American William Perry Fogg traveled the world, describing his tour in a series of letters to The Cleveland Leader newspaper, entitled, Round the World: Letters from Japan, China, India, and Egypt (1872). But long before Fogg, Greek traveller Pausanias (c. 100 AD) wrote a work that was translated into French in 1797 as Voyage autour du monde ("Around the World"). Verne's friend Jacques Arago had written a very popular Voyage autour du monde in 1853. In 1869–70 the idea of travelling around the world reached critical popular attention when three geographical breakthroughs occurred: the completion of the First Transcontinental Railroad in America (1869), the linking of the Indian railways across the sub-continent (1870), and the opening of the Suez Canal (1869). In 1871 appeared Around the World by Steam, via Pacific Railway, published by the Union Pacific Railroad Company, and an Around the World in A Hundred and Twenty Days by Edmond Planchut. In early 1870, the Erie Railway Company published a statement of routes, times, and distances detailing a trip around the globe of 23,739 miles in seventy-seven days and twenty-one hours.
Another early reference comes from the Italian traveler Giovanni Francesco Gemelli Careri. He wrote a book in 1699 that was translated into French: Voyage around the World or Voyage du Tour du Monde (1719, Paris). The novel documents his trip as one of the first Europeans to circle the world for pleasure rather than profit, using publicly available transportation. Gemelli Careri provides rich accounts of seventeenth-century civilization outside of Europe. These include Persia during the Ottoman Empire, Hindustan during the reign of Aurungzebe, the Chinese Lantern Festival and the Great Wall, and the native people of Meso-America. References to his books can be found in other historical publications like the Calcutta Review.
In 1872, Thomas Cook organised the first around-the-world tourist trip, leaving on 20 September 1872 and returning seven months later. The journey was described in a series of letters that were published in 1873 as Letter from the Sea and from Foreign Lands, Descriptive of a tour Round the World. Scholars have pointed out similarities between Verne's account and Cook's letters, although some argue that Cook's trip happened too late to influence Verne. Verne, according to a second-hand 1898 account, refers to a Cook advertisement as a source for the idea of his book. In interviews in 1894 and 1904, Verne says the source was "through reading one day in a Paris cafe" and "due merely to a tourist advertisement seen by chance in the columns of a newspaper." Around the World itself says the origins were a newspaper article. All of these point to Cook's advert as being a probable spark for the idea of the book.
The periodical Le Tour du monde (3 October 1869) contained a short piece titled "Around the World in Eighty Days", which refers to "140 miles" of railway not yet completed between Allahabad and Bombay, a central point in Verne's work. But even the Le Tour de monde article was not entirely original; it cites in its bibliography the Nouvelles Annales des Voyages, de la Géographie, de l'Histoire et de l'Archéologie (August, 1869), which also contains the title Around the World in Eighty Days in its contents page. The Nouvelles Annales were written by Conrad Malte-Brun (1775–1826) and his son Victor Adolphe Malte-Brun (1816–1889). Scholars believe that Verne was aware of the Le Tour de monde article, the Nouvelles Annales, or both, and that he consulted it and/or them, noting that the Le Tour du monde even included a trip schedule very similar to Verne's final version.
A possible inspiration was the traveller George Francis Train, who made four trips around the world, including one in 80 days in 1870. Similarities include the hiring of a private train and being imprisoned. Train later claimed, "Verne stole my thunder. I'm Phileas Fogg."
Regarding the idea of gaining a day, Verne said of its origin: "I have a great number of scientific odds and ends in my head. It was thus that, when, one day in a Paris café, I read in the Siècle that a man could travel around the world in 80 days, it immediately struck me that I could profit by a difference of meridian and make my traveller gain or lose a day in his journey. There was a dénouement ready found. The story was not written until long after. I carry ideas about in my head for years – ten, or 15 years, sometimes – before giving them form." In his April 1873 lecture, "The Meridians and the Calendar", Verne responded to a question about where the change of day actually occurred, since the international date line had only become current in 1880 and the Greenwich prime meridian was not adopted internationally until 1884. Verne cited an 1872 article in Nature, and Edgar Allan Poe's short story "Three Sundays in a Week" (1841), which was also based on going around the world and the difference in a day linked to a marriage at the end. Verne even analysed Poe's story in his Edgar Poe and His Works (1864). Poe's story "Three Sundays in a Week" was clearly the inspiration for the lost day plot device.