[2] Schreiner finished his secondary education in 1921, and enrolled at the University of Oslo where he majored in history in 1927.

In 1933 he defended his doctorate, over timber export and trade politics in the early 17th century (Nederland og Norge 1625–1650.

[1] Following the outbreak of World War II he was arrested first in February 1942, being incarcerated at Bredtveit concentration camp until March.

[3][4] In 1946 and 1947 he co-edited the two-volume book Griniboken along with August Lange, with contributions from several of the prisoner at Grini.

[7] He was decorated as Knight, First Class of the Royal Norwegian Order of St. Olav in 1965.