Dutch King Willem Alexander, Queen Maxima and their daughters Amalia (L), Ariane (C) and Alexia (R) wave to the crowd as the king celebrates his 50th birthday in Tilburg on April 27, 2017.
The king's 50th birthday happens to fall on King's Day or Koningsdag formally known as Queen' Day until King Willem-Alexander ascended to the throne in 2013 taking the reign from his mother.  / AFP PHOTO / ANP / Robin van Lonkhuijsen / Netherlands OUT        (Photo credit should read ROBIN VAN LONKHUIJSEN/AFP/Getty Images)