query: When was Sweden founded?
passage: History of Sweden
Written sources about Sweden before 1000 AD are rare and short, usually written by outsiders, and not until the 14th century are there any longer historical texts produced in Sweden. Swedish history, in contrast with pre-history, is thus usually taken to start in the 11th century, when the sources are common enough that they are possible to be contrasted with each other.
passage: Swedish festivities
The Swedish National Day on June 6 is a public holiday as of 2005, but so far there are few established traditions for this day. The celebration of this day begun as the Day of the Swedish Flag, ca 1900, and the day is chosen in commemoration of the election of Gustav Vasa as King of Sweden on this date in 1523.