The carnival season, referred to as "Fasnacht", is celebrated in Liechtenstein from Dirty Thursday through until Carnival Tuesday and is known as the "fifth season of the year". It is followed by Bonfire Sunday, traditionally the Sunday after Ash Wednesday, when a large pile of wood is set alight to drive away the winter. Liechtenstein's national day, the Prince's Day, is celebrated every year on 15 August. A holy day and a bank holiday in the Principality, it was introduced in 1940 and is closely linked to the birthday of the Reigning Prince at the time, Prince Franz-Josef II, on 16 August.