During the celestial annual journey of the Earth round the Sun, the Summer Solstice is the moment when the Sun is at its furthermost point north of the Equator.
In the Northern Hemisphere, the 2021 summer solstice is on 21 June, at 03:32 GMT.
Our Sun Time App shows the sun's seasonal position in the solar cycle right now. It is a digital yearly sundial. There are physical sundials as well, which could be called sunlight timepieces.
The word 'solstice' comes from the Latin for midsummer, expressing the idea that the sun is stopped in its ascent of the sky.
The earth's tilt means that the sun's position varies by 46° during the yearly orbit. The northerly limit is known as the Tropic of Cancer and the southerly limit is the Tropic of Capricorn.
At about 21st June the sun is directly over the Tropic of Cancer providing the northern hemisphere with its longest day. In December the southern hemisphere enjoys its summer solstice when the sun is directly above the Tropic of Capricorn.
There is strong evidence that celebration of the summer solstice goes back to the Neolithic period as so many monuments seem to align with the summer sunrise.
In England the great circle known as Stonehenge has an alignment of stones marking sunrise on the longest day. Sadly, we have no idea how the henge was actually used, but we can be sure that its builders were astronomers.
To find out more about Stonehenge go to site of English Heritage.
Human habitation reaches higher latitudes in the northern hemisphere. People cannot sleep during the midsummer nights when it does not get completely dark.
Many Scandinavian communities have feasts, folk music and dance. Some festivals are held on the solstice and others on the Feast of St John. In Britain St John's day is called Midsummer's day.
The association of magic with midsummer in English culture is exemplified by Shakespeare's delightful comedy "A Midsummer Night's Dream".
In the play normality is turned upside-down and fairies interfere with human affairs. The woodland setting becomes an enchanted place with supernatural rulers.
Dates for equinoxes and solstices in the Northern and Southern Hemispheres are the same, but in opposite seasons. For example, the Summer Solstice north of the Equator is mirrored south of the Equator by the Winter Solstice.
Find below precise solstice and equinox dates and times for the Northern Hemisphere, from 2016 to 2021.