Final answer:
Midsummer in Sweden is celebrated on Midsummer's Eve with outdoor festivities, coinciding with the summer solstice when days are longest.
Step-by-step explanation:
In Sweden, Midsummer is celebrated on the eve of Midsummer Day, which is around June 21st, the summer solstice. This celebration is traditionally an outdoor event due to the long days and warm weather associated with the solstice. Families and friends gather in the open air to enjoy festivities, which include dancing around the maypole, singing songs, and sharing a feast. While some activities might take place indoors, the majority of the Midsummer events are held outside, embracing the full experience of the longest day of the year.