add feast day with references;
'''Hallvard Vebjørnsson of Norway''' (Hallvard Den Hellige) (c. 1020–1043)
, commonly referred to as Saint Hallvard, is the [[patron saint]] of Oslo, Norway. He is considered a [[martyr]] because of his defence of an innocent woman.
St. Hallvard was celebrated as a local saint in Norway - and especially in the eastern region - throughout the Middle Ages. His
religious feast day was [[May 15]]. Hallvard has been revered as a martyr for his defence of an innocent person since medieval times.
Hallvard's Cathedral (Hallvardskatedralen), a [[cathedral]] dedicated to his name was finished in Oslo in 1130, where his [[relics]] were stored.
The connection of St. Hallvard to the city of Oslo was fortified by the fact that his image was recorded in the city's seal already on the 14th century. The municipality's highest honor, the St. Hallvard Medal (St. Hallvard-medaljen), was named after him in 1950.