We know (from the first sentence of Chapter 2.X) that Aline's frank talk with Mme. de Sautron took place on a Sunday in March, and the "fracas" was the next day, Monday.  But it seems impossible to determine the precise date.

There's one faint indication that the Fracas took place earlier rather than later in March: André-Louis refers to the uprising in Rennes, which took place in January, as having happened "a few short weeks ago".  And we might eliminate Sunday March 30 altogether since it was Passion Sunday and perhaps an unlikely day for Aline to break her silence.

Clearly we need further information, possibly to be obtained from the contemporary news accounts that, we know, "reported in considerable detail the fracas at the Theatre Feydau" [Chapter 3.I].  It might also prove fruitful to investigate the history of the Salle Feydeau in Paris, built in 1789.  Perhaps the Theatre Feydeau of Nantes closed permanently and moved to this new location?