21st of June is the longest day- we in Britain are different to the rest of the world in that we take the longest day to be midsummers day. June the 24th is a church quarter day and is the feast of John the Baptist- the closest feast day to the actual summer solstice so was adapted by the church as Midsummers Day- another case of the Christian Church hijacking pagan feast days!!!!
It always amuses me that scientists, (climatologists, geographers or whatever) contend that 'summer' actually begins at the time of the solstice on June 21/22. On that basis, if the 24th is - as traditionally claimed - Midsummer's Day, then June 27th must be the first day of autumn. In Britain, it often is, of course!