Dates on the grid are guideposts. Ancient calendars, local seasons, and contemporary traditions differ; the linked sources explain what is attested and what is a modern choice.
Astronomical marker · Usually June 20–22
June solstice / Midsummer
The longest northern daylight and a welcome occasion for outdoor fellowship. Modern Midsummer customs vary widely.
The astronomical solstice and a specific ancient Norse religious festival should not be assumed identical.