1909 was a year in the 20th century.
- Back to the Future: The Game stated that Arthur was about 29 in 1931. That might not be possible due to William being born in 1885, as he would only be 17 in 1902 when Arthur was born.
- As stated on Arthur's page, The Game dialogue as stated by Emmett Brown said he graduated from high school five years before him. Since Emmett was born in 1914, this further supports Arthur being born this year.