we believe the custom of bonfires at St John's eve derived from the summer solstice bonfire ... the date has been moved. And quite possibly the July 12 bonfires replaced that in parts of Northern Ireland. And from the July 12 bonfires probably came the Aug 12 Loyalist bonfires in Derry (Apprentice Boys commemoration) and in response to that Aug 15 Feast of the Immaculate Conception bonfires in Derry on the other side of the sectarian divide![in the last couple of years this custom has declined due to community leaders' concerns about environment and safety - street parties are replacing the bonefires)But the St John's eve custom does survive in many places.