The flag for the Kingdom of the Netherlands is a red, white and blue tricolour whose origins lie in the second half of the 16th century when Prince William of Orange led the revolt against the Spanish. It was officially adopted on 19 February 1937, and in 1958 the colours were precisely defined as bright vermilion and cobalt blue. There are specific days when the Dutch flag is flown from public buildings, such as Liberation Day and Armistice Day, and it is also flown on royal occasions and birthdays, when an orange penant flies above it. Many Dutch cities and regions also have their own flags. Amsterdam’s red-black-red horizontal stripes with three white St Andrew's crosses are almost as well known as the stripes of the national flag.