If he had just said “several years ago” I’d get it. That’s a massive political shift that didn’t happen overnight, Battle Endor may have been the fall of the empire, but the Empire still existed. It took time for the New Republic to form and then wrest control.

In the same way that Rome didn’t disappear overnight.

But because he said “on this day” it means this planet/sector has chosen a specific date, which would include a year.