As a country whose summer is relatively short, it's no surprise that Sweden goes all out for Midsommar. This celebration of the Summer Solstice lasts a few days (technically the longest day of this year is Tuesday, June 21st, but the Swedes will celebrate Midsummer's Eve or Midsommarafton and Midsummer's Day, Midsommardagen, on the following Friday and Saturday.) Of course when the sun doesn't set until the wee hours, my feeling is that every day should be a party.
Traditionally, Midsommar was believed to be a magical day. Young girls would collect flowers and put them under their pillows, hoping to dream of their future husbands. Erecting maypoles and dancing around them has been mostly replaced by eating and drinking, though that still sounds pretty magical to me.