When you search for your Scandinavian ancestors in early church records you will find dates listed as feast days. The feast days were religious holidays. To find the correct modern date equivalent, you need to consult a feast day calendar.
Be aware that Scandinavian countries changed from using the Julian calendar to the Gregorian calendar in the 1700s. For information on these calendars, see the Julian and Gregorian Calendars article in the FamilySearch Research Wiki.
If an event such as a christening occurred on a feast day, the scribe typically would record the event as occurring on the name of the feast day rather than the actual day and month. For example, the date “1795 Dom. 14 p. Trin.” is also September 6th, 1795, according to the feast day calendar.
There were two kinds of feast days, fixed and moveable. An example of a fixed feast day is Christmas, which is always on December 25th. Easter is an example of a moveable feast day. The actual date of Easter each year is determined by astronomical factors, and differs from year to year.
You can find feast day calendars for the Scandinavian countries in the FamilySearch Research Wiki. Search for “Moveable Feast Day Calendar” and “Fixed and Moveable Feast Days” for the country you are researching. For example:
When you search “Moveable Feast Day Calendar” you will be able to click on the year of your choice and then see the date of the record you found. When you search “Fixed and Movable Feast Days” you will see that the information is listed by the first letter of the name of the feast day. You will be able to find the feast day by clicking on that letter. Each month is also listed, and if you know the month for the record you are searching, you will be able to click on the month to find your feast day with the correct date.