In many of the old Norwegian church and parish records they use the liturgical church date. This page explains those dates:

http://homepages.rootsweb.ancestry.com/~norway/ecclesiastical.html

While this page at family search tells you when the liturgical date fell for each specific year from 1501-1900

http://familysearch.org/learn/wiki/en/Moveable_Feast_Day_Calendar_for_Norway