Le Weekend et Le Jour Férié

Roger, 

As a general rule, France does not substitute other days in replacement of public holidays that fall on weekends. There are a number of the holidays that always fall on a nominated weekday, but those that are on a fixed date are always on that date, with no other nominated day off. 

As always, there may be occasional local/regional exceptions or agreements in specific employment agreements, but it is not a standard practice to get a day off in lieu.