What day of the week was May 21, 1871?

The day of the week May 21st, 1871 fell on was a Sunday.

French troops invade the Paris Commune and engage its residents in street fighting. By the close of "Bloody Week" the some 20,000 communards have been killed and 38,000 arrested. Opening of the first rack railway in Europe the the Rigi-Bahnen on Mount Rigi.