Today, Saturday June 23rd is Midsummernight Eve in Norway, also known as 'St.Hans Aften' or 'Jonsok-kveld', depending on where you are in the country. Huge bonfires will be burned as part of the celebrations. St. Hans or Jonsok both reveal that the festival has been named after St. John the Baptist, as the 24th is his birthday according to the Festival Calendar of the pre-reformation Church.
As with so many of the church festivals, it was introduced in order to replace an old heathen festival on that same date, thought to be the Summer Solstice, or the longest day of the year.
In Norway, the evening is celebrated with partying, good food, music and dancing, and the burning of huge bonfires. The burning of bonfires has of course survived from heathen times, when it was believed that the fire had special cleansing powers, and was also used to drive away evil powers, witches included.
Medical herbs also had special powers at Midsummernight, and so did water. Dew that fell on that night was believed to have healing properties, particularly for ailments of the eyes.
Midsummernight Eve was a public holiday in Norway until 1771, and has as a matter of fact survived as a day off in several communities to this day.