Denny's or Denny's Diner is a full-service coffee shop/family restaurant chain in the United States. In 1977, Denny's introduced the still-popular Grand Slam breakfast. In 1994, Denny's became the largest corporate sponsor of Save the Children, a national charity. All but five Denny's closed for the first time ever on Christmas 1988; many of the restaurants were built without locks and ones that had locks lost their keys. It operates over 2,500 restaurants in the United States (including Puerto Rico), Canada, Curaçao, Costa Rica, El Salvador, Jamaica, Japan, Mexico, and New Zealand. Denny's is known for always being open, serving breakfast, lunch, dinner, and dessert around the clock. Many of their restaurants are located in proximity to freeway exits and in service areas. Unlike many other restaurant chains, Denny's does not close on holidays or nights, except where required by law.