Since after Treehouse of Horror X back in Fall 1999, FOX somehow started airing Treehouse of Horror in November for a whole decade(aka 10 Years) starting with the premiere of Treehouse of Horror XI back in Fall 2000. Until FOX went back to airing Treehouse of Horror in October starting with the premiere of Treehouse of Horror XX back in Fall 2009, but then FOX went back to airing Treehouse of Horror in November starting with the premiere of Treehouse of Horror XXI back in Fall 2010. FOX went back to airing Treehouse of Horror in October starting with the premiere of Treehouse of Horror XXII back in Fall 2011, but then FOX went back to airing Treehouse of Horror in November starting with the premiere of Treehouse of Horror XXXI back in Fall 2020(coincidentally, Treehouse of Horror XXXI aired in Canada before it aired in the United States). FOX went back to airing Treehouse of Horror in October starting with the premiere of Treehouse of Horror XXXII, but then FOX went back to airing Treehouse of Horror in November starting with the premiere of Treehouse of Horror XXXIV back in Fall 2023. Starting October 19, 2025, FOX will return to airing Treehouse of Horror in October, starting with the premiere of Treehouse of Horror XXXVI.