Final preparations were underway in the Netherlands on Sunday ahead of the inauguration of the country's new King. Thousands of workers were completing stages, stands and event tents in central Amsterdam, with hundreds of trucks transporting materials and supplies, De Telegraaf reported. Buildings were being decorated in the red-white-blue colors of the Dutch flag and the orange of the royal house. "Orange fever" has gripped the Netherlands, DPA cited the daily as saying. Amsterdam attracts some 700,000 visitors on a regular Queen's Day, a national holiday celebrated annually since 1948 on the birthday of late former queen Juliana, Queen Beatrix's mother and predecessor. Even more are expected on Tuesday for Beatrix's abdication and succession by her eldest son, Willem Alexander, who will be the country's first male monarch in 122 years. Beatrix kept April 30 - normally a sunny spring day - as the date for the national holiday, both as a tribute to her mother and because her own birthday is in January. As of 2014, Queen's Day will become King's Day and will be celebrated on April 27, Willem-Alexander's birthday. Beatrix, 75, announced in January her plan to stand down. She chose Queen's Day to sign the Abdication Act in the Royal Palace, on Amsterdam's Dam Square. Under Dutch law, her signature immediately makes Crown Prince Willem Alexander the next king. He will therefore not be crowned, but "inaugurated" in the adjacent Nieuwe Kerk, where he will take an oath to observe the constitution and serve the Dutch. Millions are to attend street parties and free markets throughout the Netherlands. Willem-Alexander celebrated his 46th birthday with family and friends on Saturday.