Thousands of Dutch decked in orange lined the streets on Saturday as the Netherlands celebrated its first-ever "Kings Day" in honour of Willem-Alexander, inaugurated one year ago.
The popular King and his Argentinian-born wife, Queen Maxima, were greeted by thousands of enthusiastic fans in the northwestern fishing town of De Rijp, where they took part in a number of traditional Dutch games.
Queen Maxima hit a ball into the mouth of a mock-up whale -- symbol of the town's past as a whale processing centre -- to thunderous applause before moving on to gather flowers from a myriad of well-wishers.
From there the royal procession, which also included the king's mother Princes Beatrix, who abdicated last year after 33 years on the throne, traveled south to Amstelveen near Amsterdam.
Willem-Alexander, 46, was sworn in on April 30 last year, the first Dutch king in more than 120 years and the first of a wave of relatively youthful European monarchs.
Saturday marked the first-ever "King's Day" celebration, a tradition introduced during the reign of a succession of Dutch queens, starting around 1890.
The day celebrates the monarch's birthday with Willem-Alexander's being on Sunday, and sees the country turn orange as the Dutch don hats, shirs, scarves, sunglasses and other paraphernalia in the colour of the Royal House.
Although the monarchy is popular in the Netherlands, some question the cost of the royal household and republicans are seeking a reduction to the king's tax-free salary of 825,000 euros (about $1.1 million).
A survey published on Saturday by the NOS public broadcaster said 74 percent of those Dutch questioned said they trusted the King.
Meanwhile, the government's information service (RVD) on Saturday unveiled the Royal House's first-ever page on social media website Facebook.
The introduction of technology is part of a "quiet revolution happening at the Palace," Dutch centre-left newspaper De Volkskrant said this week.
"Beatrix never sent an email and had a mobile phone for only six years. After the King's inauguration his whole court is now armed with iPads and iPhones," the paper said.
Even web search giant Google took a bow on Saturday, sporting a royal orange theme for its Dutch search engine, www.google.nl.