November 6 is Gustavus Adolphus Day, one more official flag day in Sweden and Finland. The day commemorates the death of King Gustavus Adolphus of Sweden, who was killed at the Battle of Lützen in the Thirty Years' War.

King Gustavus Adolphus was killed in 1632 during the Battle of Lützen. The date of his death is actually November 16, not 6. At the time of his death Sweden used the Julian calendar (old style). Later Sweden started using the Gregorian calendar, but original date of king's death is still used now.

The remains of the old tradition are only consumption of special cakes with a chocolate or marzipan relief of the king on the top. Gustavus Adolphus pastry (Gustav Adolfsbakelse) is a pastry traditionally eaten every 6 November in Sweden, Gustavus Adolphus Day, the death day of King Gustavus Adolphus the Great. It is especially popular in Gothenburg, a city founded by the king.