According to MusicSack (quoting Kurzgefasstes Tonkunstler Lexikon fur Musiker und Freunde der Musik?), 1861 is the birthyear of another composer with surname Michiels, while Gustave was born around 1845 in Belgium. November 17, 1911 death date from BNF. Other sources give December only.
Update: Currently (2020) MusicSack mentions 1845 as birth year. Worldcat mentions publications from 1870 on, so that 1861 seems less probable as birth year.