Summer solstice
The summer solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere (Northern and Southern). For that hemisphere, the summer solstice is the day with the longest period of daylight and shortest night of the year, when the Sun is at its highest position in the sky. At either pole there is continuous daylight at the time of its summer solstice. The opposite event is the winter solstice.
Although the summer solstice is the longest day of the year for that hemisphere, the dates of earliest sunrise and latest sunset vary by a few days.[8] This is because Earth orbits the Sun in an ellipse, and its orbital speed varies slightly during the year.
Midsummer
There is evidence that the summer solstice has been culturally important since the Neolithic era. Many ancient monuments in Europe especially, as well as parts of the Middle East, Asia and the Americas, are aligned with the sunrise or sunset on the summer solstice.
The significance of the summer solstice has varied among cultures, but most recognize the event in some way with holidays, festivals, and rituals around that time with themes of fertility. In the Roman Empire, the traditional date of the summer solstice was 24 June. In Germanic-speaking cultures, the time around the summer solstice is called 'midsummer'.
In northern Europe, midsummer was traditionally reckoned as the night of 23–24 June, with summer beginning on May Day. The summer solstice continues to be seen as the middle of summer in many European cultures, but in some cultures or calendars it is seen as summer's beginning. In Sweden, midsummer is one of the year's major holidays when the country closes down as much as during Christmas.
Neopagan traditions
Midsummer has pagan pre-Christian roots in Europe. As forms of Neopaganism have widely different origins, observances can vary considerably despite the shared name. Some celebrate in a manner as close as possible to how they believe ancient pagans observed the summer solstice, while others observe the holiday with rituals culled from numerous other unrelated sources.
At the ancient monument of Stonehenge, in the English county of Wiltshire, many people gather to observe the sunrise alignment with the stones on the summer solstice.