Dutch King Willem-Alexander (1st R, front) attends the King's Day celebration in Amersfoort, the Netherlands, April 27, 2019. The King's Day is a national holiday in the Netherlands, marking the birth of King Willem-Alexander. (Photos: Xinhua)

Dutch King Willem-Alexander (2nd L, front) and his family celebrate the King's Day in Amersfoort, the Netherlands, April 27, 2019. The King's Day is a national holiday in the Netherlands, marking the birth of King Willem-Alexander.

Dutch King Willem-Alexander and his family celebrate the King's Day in Amersfoort, the Netherlands, April 27, 2019. The King's Day is a national holiday in the Netherlands, marking the birth of King Willem-Alexander.

Dutch King Willem-Alexander (front) waves onstage during the King's Day celebration in Amersfoort, the Netherlands, April 27, 2019. The King's Day is a national holiday in the Netherlands, marking the birth of King Willem-Alexander.

Dutch King Willem-Alexander (front) speaks onstage during the King's Day celebration in Amersfoort, the Netherlands, April 27, 2019. The King's Day is a national holiday in the Netherlands, marking the birth of King Willem-Alexander.