The basic arms of Sweden are three gold crowns on blue, and these gave rise to the colors of the current flag, which dates from the accession of King Gustavus I Vasa.
The form is based on that of Sweden although the construction is somewhat different.
As in the kingdom of Denmark, there is a swallow-tail version used for official display(s), but this variant shape has a pointed tongue (an extension of the cross). It was in fact reserved for state purposes back in 1663. The cross is used to divide the quarters of the royal shield.
Swedish Flag Day is celebrated on 6 June, the anniversary of the accession of King Gustav. From 1844 to 1906 the canton of the flag contained the Swedish-Norwegian union mark.
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