This idea of the sun of the day having its opposite in the night is an archetypal idea.
Pythagoras, for example, thought that the earth had a twin.
The idea also comes out in an anonymous book that was published during the war.
This book was called Peter Blobbs—Real Dreams, and the first dream, the one in which the midnight sun analogy appears, is called “The Night of the Swinging Censer.”
The dreamer is in an old cathedral which slowly fills with people.
It is sunset time or after.
In the middle of the cathedral there hangs a censer which is swinging to and fro.
The more the night advances, the stronger grow the oscillations, and at the same time the church fills with hundreds of people clad in the costumes of all times and of all centuries.
Finally even the primitives come in.
As the church fills, the censer swings more and more and glows more brightly.
At midnight the maximum is reached, and towards morning it decreases; with sunrise it comes to a standstill. ~Carl Jung, Seminar 1925, Page 67.
Carl Jung across the web: