 This explanation is questionable because in the Middle Ages the solstice took place around the middle of June due to the inaccuracy of the Julian calendar.It was only in 1582, through the Gregorian calendar reform, that the solstice returned to June 21 as it had been in the fourth century.Therefore, a more likely reason why the festival falls on June 24 lies in the Roman way of counting, which proceeded backward from the Kalends (first day) of the succeeding month.