Encouraged by commerce, the secular celebration of Christmas is popular in Japan, though Christmas is not a national holiday. Gifts are sometimes exchanged. Christmas parties are held around Christmas Day; Japanese Christmas cake, a white sponge cake covered with cream and decorated with strawberries, is often consumed and Stollen cake, either imported or made locally, is widely available. Christmas lights decorate cities, and Christmas trees adorn living areas and malls. Christmas Eve has become a holiday for couples to spend time together and exchange gifts. A successful advertising campaign in the 1970s made eating at KFC around Christmas a national custom. Its chicken meals are so popular during the season that stores take reservations months in advance.