We know that it's still April ("the April dusk", Chapter VII) and a Monday,
since the next day Corbal explicitly declares that it's Tuesday.
But Chauvinière arrives in Poussignot "toward the end of April" [Chapter V],
and that was at least ten days ago, the time it took to pass the anti-celibacy
law! So surely Corbal's sentencing is the last Monday in April.