A very Happy National Day to Sweds this 6 June 2017. Although a fairly new recognized holiday–only being celebrated as a public holiday in 2005, and before 1983 it was Flag Day–nevertheless it coincides with the date of the election of King Gustav Vasa in 1523 and the adoption of a new Constitution in 1809. A nice description of the Holiday can be found here. There are not a lot of significant traditions with the holiday, but it sets the stage for the big summer holiday in two weeks, Midsommer!