Midsummer, also known as St John's Day, is the period of time centered upon the Summer Solstice, and the Northern European celebrations that have accompanied it. The actual astronomical solstice occurs on or about June 20th each year (the first "day" of summer) while many celebrations take place on a day between June 19 and June 25 and the preceding evening. The exact dates vary between different cultures. Some time ago, the Christian Church designated June 24 as the feast day of the St John the Baptist. The observance of St John's Day begins the evening before, known as St John's Eve.
It is likewise that the Christian Church set the date of Christmas - the day we celebrate the Incarnation of Christ (December 25th). That date is related to the Winter Solstice, which occurs days before. By the 25th of December, we can perceive that the days begins to lengthen. St. John the Baptist’s day occurs a few days after the Summer Solstice when we can notice the days begin to be shorter in similar manner. The choice of the days has to do with the saying attributed to John the Baptist in the gospel of John: “I must decrease that he may increase” (John 3:30). Thus as the days grow shorter we begin to look for the coming of Christ, the Light of the World. Thus, when Christ arrives, the days begin to lengthen again.
Although Midsummer is originally a pagan holiday, in Christianity it is associated with the nativity of John the Baptist, which is observed on the same day, June 24, in the Catholic, Orthodox and some Protestant churches. It is six months before Christmas because Luke 1:26 and Luke 1.36 imply that John the Baptist was born six months earlier than Jesus, even though the Bible does not say at which time of the year this happened.
The Summer Solstice and the Feast of the Nativity of John the Baptist are celebrated by many Christian denominations. In Sweden, for instance, Midsummer is such an important festivity that there have been serious discussions to make the Midsummer's Eve into the National Day of Sweden. However, many European midsummer-related holidays, traditions, and celebrations are often pre-Christian in origin. They are particularly important in geographic Northern Europe – especially Scandinavian counties where the interplay of light and dark in relation to the seasons of the year is quite dramatic. It is also very strongly observed in Poland, Russia, Belarus, Germany, Netherlands, Ireland, parts of the United Kingdom (Cornwall especially), France, Italy, Malta, Portugal, Spain, Ukraine, other parts of Europe, and elsewhere – such as Canada, the United States, Puerto Rico.
In any event, the coming of the Summer Solstice reminds all of us of the continual cycle of the seasons and the passing of time. For those of us in the Northern hemisphere, it is a reminder that we should “make hay while the sun shines” for soon enough, the days will shorten, the cold will return and we will once more depend on our careful stewardship of the summer’s plenty to help us through the darker days of winter. This is still good advice, even though modern conveniences lessen our dependence on seasonal produce - whenever we experience light and joy, we should celebrate and store up so that when "darker" days ensue, we are prepared and ready.