holidays
Saint John's Eve and the first day of the Midsummer celebrations (although this is not the real summer solstice; see June 20) (Roman Catholic Church, Europe): Kupala Night (Belarus, Lithuania, Poland, Russia, Ukraine)
Related Wikipedia articles
Kupala Night
Traditional Slavic holiday
Kupala Night is one of the major folk holidays in some of the Slavic countries that coincides with the Christian feast of the Nativity of St. John the Baptist and the East Slavic feast of Saint John's Eve. In folk tradition, it was revered as the day of the summer solstice and…Source: Wikipedia (CC BY-SA)
June 23
Day of the year
June 23 is the 174th day of the year in the Gregorian calendar; 191 days remain until the end of the year.Source: Wikipedia (CC BY-SA)