Now Hiring - Great pay & Benefits. Click to Apply. About Denny's Denny's is an American diner chain that is known for being open 24 hours a day, serving breakfast, lunch and dinner. Known in some locations as "Denny's Diner", Denny's operates more than 1600 locations throughout the US, Canada, Mexico, New Zealand and a number of other countries. Most often located just adjacent to highways or on main thoroughfares, Denny's attracts customers young and old. First opened as Danny_s Donuts in 1954 in Lakewood, California, the name was changed to Denny's in 1959. Its popular 'Grand Slam' breakfast was introduced in 1977 and remains a popular menu item today.