The sentence arrived thirty years later
On this day, 20 September 1792: the cannonade at Valmy. Two armies of nearly equal size (36,000 French, 34,000 Prussians) stood off and fired artillery at each other for an afternoon. About 300 French casualties, about 200 Prussian. Then the Prussians pulled back, their retreat dogged by food shortages and dysentery, and the Republic was proclaimed the next day.
The line everyone quotes is Goethe's, watching from the Prussian side: “Here and today a new epoch in the history of the world has begun.” He wrote it down in 1822. Thirty years after the fact. What he set down at the time was smaller: ten thousand shots a side that day, two hundred of our men down, “and uselessly.”
One more wrinkle. The citizen army that supposedly won Valmy was at least half professional soldiers, and the artillery that did the actual work was the best in Europe.
The citizens got the sentence. The gunners got the day.
(Sources: Wikipedia, Battle of Valmy, with its citations to Schama and Wainwright's “The cannonade of Valmy”; Goethe's Kampagne in Frankreich 1792, written 1819-1822, first printed 1822.)