Today is Fullveldisdagurinn – or ‘Sovereignty Day’. Iceland became a separate state on 1st December 1918 with its own flag, though was still a part of the Kingdom of Denmark. Denmark continued to look after it’s foreign affairs and defence interests until Iceland gained its complete independence in 1944.
Although not an official holiday, many Icelanders celebrate Sovereignty Day, especially Icelanders living abroad.
Read more about Icelandic Holidays here