On this day 90 years ago (23 February 1934) Prince Leopold, the Duke of Brabant, became King Leopold III, the 4th King of the Belgians, 6 days after his father's sudden death.
A depiction of his swearing-in ceremony in a tapestry from 1947:
On this day, 65 years ago (12 April 1959), the engagement announcement of Prince Albert, Prince of Liège to Donna Paola Ruffo di Calabria.
A pic from that day, taken by King Baudouin (it was shared by the Royal Palace in 2019, for their 60th wedding anniversary):