In both the movie and the novel, when Venkat (Vincent) Kapoor is trying to persuade Teddy Sanders to allow satellite imagery of the Ares 3 site, Sanders says that Ares 4 wouldn't launch for another five years.
Every other reference I have been able to find says that Ares 4 would be four years after Ares 3. Given the recent 'death' of Watney, Sanders would presumably be up-to-date on the Ares missions. If the Ares 4 mission had been delayed because of to Watney's death, there would presumably be a later reference, if only to note that Ares 4 was back on the original schedule so they could rescue Watney. A Martian year is almost two Earth years, so it isn't a difference in which planet's years are being referred to.
Yet this line has lasted from the pre-publish version of the story, into the printed version, and survived intact in the movie.
Why would Sanders have a different launch date?