One day classic

The classic cycle races are the most prestigious one-day professional cycling road races in the international calendar. All of these events run in western Europe, have been fixtures on the professional calendar for decades and the oldest ones date back to the 19th century. They are normally held at roughly the same time each year. The five most revered races are often described as the 'Monuments'.

For the 2005 to 2007 seasons, the Classics formed part of the UCI ProTour run by the Union Cycliste Internationale. This event series also included various stage races including the Tour de France, Giro d'Italia, Vuelta a España, Paris–Nice and the Critérium du Dauphiné Libéré, and various non-Classic one-day events. The ProTour replaced the UCI Road World Cup series which contained only one-day races. Many of the Classics, and all the Grand Tours, were not part of the ProTour for the 2008 season because of disputes between the UCI and the ASO, which organizes the Tour de France and several other major races.

Although cycling fans and sports media eagerly use the term "classic", there is no clear consensus about what constitutes a classic cycling race. UCI, the international governing body of cycling, has no mention at all of the term in its rulings. This poses problems to define the characteristics of these races and makes it impossible to make precise lists. Several criteria are used to denote the importance of a cycling race: date of creation, historical importance and tradition, commercial importance, location, level of difficulty, level of competition field, etc. However, many of these paradigms tend to shift over time and are often opinions of a personal nature. One of the few objective criteria is the official categorization of races as classified by the UCI, although this is not a defining feature either, as many fans dispute the presence of some of the highest-categorized races and some older races are not included in the UCI World Tour.

...
Wikipedia