What day of the week was September 19, 1870?

The day of the week September 19th, 1870 fell on was a Monday.

Franco-Prussian War: the Siege of Paris begins the which will result on January 28, 1871 in the surrender of Paris and a decisive Prussian victory. Having invaded the Papal States a week earlier the the Italian Army lays siege to Rome, entering the city the next day, after which the Pope described himself as a Prisoner in the Vatican.