Swimmers and hikers enjoy solstice

A significant story is unfolding on the international scene. In pictures: Swimmers and hikers enjoy solstice4 hours ago Share Save Add as preferred on GoogleSue PazandLisa YoungBBCThousands gathered at Stonehenge in Wiltshire to watch the sunriseSummer solstice is being celebrated across the northern hemisphere, marking the start of astronomical summer. While we generally think of it as the whole day, it actually happens at a single moment when the hemisphere's pole is tilted at its maximum angle towards the Sun. That exact time this year is Sunday 21 June at 09:24 BST.

Its significance is reflected at monuments and in rituals around the world. We have selected some images from across the UK to mark the event. BBCWeatherWatcher/Daniel RivePhil Maclean Sunrise brought a dramatic display of red and orange hues in St Martin, JerseyMore than 200 people took part in a solstice walk from The Valley Evesham to New Farm Nature Reserve in WorcestershireThe solstice always occurs between 20 and 22 June, though during a leap year it generally falls on 20 June.

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The exact date shifts slightly each year because the Earth takes almost a quarter of a day longer to complete its orbit of the Sun than our calendar accounts for. This discrepancy is why we add a leap day every four years – to keep the calendar aligned with Earth's orbit. In English, the world solstice comes from the Latin word solstitium, meaning "sun standing still".

It seems to suggest a brief pause as the Sun reaches its most extreme point. Janet Burns, Linda Candlish, Trish Bromley and Gill Richardson from County Durham dressed up for the occasion at Roker Beach in SunderlandDespite the fog, the Hornsea Mermaids made the most of an early dipMore on this story What is the summer solstice and why is it the longest day of the year? When is the winter solstice?

The development has drawn wide international attention, with diplomatic circles watching closely.