La Toussaint (All Saints’ Day), is celebrated on November 1st, and is a jours férié (public holiday). However, if la Toussaint falls on a Tuesday, then Monday becomes an unofficial day off too because it’s generally considered a bit pointless to have the weekend off, go into work for one day, and then have another day off. If la Toussaint falls on a Thursday, then Friday is usually taken off as well for the same reason.
Everywhere – other than flower shops, cemeteries, and churches – tends to be closed, even museums, galleries, restaurants, and bars. This time off work is to enable people to attend religious services, to honor their dead and the saints, and to spend time with their families. Unlike in the US, public holidays are not an excuse for businesses to have sales and special offers!
Traditionally, people visit the graves of their loved ones, and place pots of chrysanthemums upon them, hence the florists staying open. In fact, at this time, the windows of flower shops will be chock-full of these graveside flowers.
By the way, do not on any account, ever present chrysanthemums as a gift to anyone in France – they are considered to be funereal. At best, it would be thought of as odd, and at worst, it would be offensive.