St. Olav's Eve (Ólavsøkuaftan) is part of a two-day celebration that begins in the evening of July 28th.
Olaf II Haraldsson (Ólavur Halgi in Faroese) was King of Norway from 1015 to 1028. Olaf died on July 29th 1030 in the battle at Stiklastað in Norway. There are many sagas about miracles performed by Olav and within a year of his death, he had been canonised as a saint.
Shortly after, Nidaros Cathedral in Trondheim was built over his burial site. His sainthood brought many pilgrims to the Cathedral and encouraged the widespread adoption of the Christian religion across Norway, which the Faroe Islands were part of during the middle ages.
St. Olav became the patron saint of Norway and his feast day was a major festival in Norway up until the reformation. Though the anniversary of his death is still marked in Norway by religious services, it is in the Faroe Islands where the celebrations remain a popular summer festival.