These are the days that Reindeer love — Polar Days

These are the days that Reindeer love 1
And pranks the Northern star-
This is the Sun's objective,
And Finland of the Year.
(F.1705/J.1696)
[1] days, Reindeer love:: polar days, days of 24-hour sunshine.
[2] pranks, Northern star:: the midnight sun causes the northern star hard to see.
[3] objective:: sun's object to occupy the entire 24 hours.
[4] Finland:: a land of the midnight sun.

In the extreme north of Finland may be seen the phenomenon still more grandly displayed in Lapland—a midnight sun. ─ The New Monthly Magazine (1855)

The Land of the Midnight Sun. Within the Arctic Circle-Peculiarities of the Norwegian Coast and of the People. ─ New York Times - Aug 6, 1877