The Summer Solstice is the longest day of the year.
In the northern hemisphere - where the UK is - it falls on June 21.
The Summer Solstice marks the end of Spring and start of Summer. It will end with the Autumn Equinox, which this year falls on 23 September.
It will take place at exactly 15:54 on Friday 21 June. The UK will be treated to 16 hours and 38 minutes of daylight on the day.
The Sun will rise at 4.43am and setting in the evening at 9.21pm.
What makes the solstice the longest day of the year?
We get the most hours of daylight on this day because of the position of the Earth in relation to the Sun.
It occurs when the Earth's geographical pole on either the northern or southern hemisphere becomes most inclined towards the Sun.
When the Summer Solstice takes place in the northern hemisphere, the Sun will reach its highest possible point.
As a result, the day on which the summer solstice falls will have the longest period of daylight of the year.
Our planet does not spin on a vertical axis - it is titled. This means the amount of sunlight that reaches different regions of the Earth changes during the year as it orbits the Sun.
Why doesn't the sun set in some parts of the world?
Around the time of the summer solstice areas of Norway, Finland, Greenland, Alaska and other polar regions experience 'midnight sun'.
In the Arctic Circle the sun does not set at all!
Again it comes down to the tilt of the Earth's axis.
Summer solstice is celebrated by thousands of pagans across the world.
Many gather at Stonehenge which is believed to have been used as an important religious site by early Britons 4,000 years ago.
On the summer solstice, the central Altar stone at Stonehenge aligns with the Heel stone, the Slaughter stone and the rising sun to the north east.