June 11Before England adopted the Gregorian calendar in 1752, June 11 was the day of the Summer Solstice. In addition to being the longest day of the year, it was also St. Barnabas's Day (or Barnaby Day ), and this association gave rise to the old English jingle, "Barnaby bright, Barnaby bright, the longest day and the shortest night." It was customary on this day for the priests and clerks in the Church of England to wear garlands of roses and to decorate the church with them. Other names for this day were Long Barnaby and Barnaby Bright .
SOURCES:
BkDays-1864, vol. I, p. 769
DaysCustFaith-1957, p. 143
DictDays-1988, pp. 9, 69, 100
OxYear-1999, p. 245