The summer solstice — around June 20–21 in the Northern Hemisphere — is the longest day of the year, when Earth's tilt leans your half of the planet closest to the sun. This countdown targets the next one.
The solstice is a precise astronomical moment: the sun reaches its northernmost point in the sky. Above the Arctic Circle it doesn't set at all — the midnight sun — while the Southern Hemisphere marks its shortest day.
Thousands gather at Stonehenge, whose stones align with the solstice sunrise. Sweden's Midsummer is practically a national holiday of maypoles and flower crowns, and bonfires burn across northern Europe — traditions older than written history.