This guide explains what is a solstice? the longest and shortest days explained in plain language, with the exact figures and how to work them out yourself.
A solstice is the moment Earth’s tilt leans most directly toward or away from the sun. Around 20–21 June, the North Pole tips sunward at its maximum 23.4 degrees: the sun stands overhead at the Tropic of Cancer, the northern hemisphere gets its longest day, and the southern its shortest. Around 21–22 December the roles reverse, with the sun overhead at the Tropic of Capricorn. The word comes from Latin solstitium — “sun standing still” — because the sun’s rising and setting points, which migrate along the horizon all year, pause and reverse direction at these dates.
How extreme the solstice feels depends entirely on latitude. At the equator, the longest and shortest days differ by only minutes. London swings from about 16 hours 38 minutes of June daylight to under 8 in December; Reykjavik from about 21 hours to 4. Above the Arctic Circle the sun simply refuses to set at the June solstice — the midnight sun — and refuses to rise in December, the polar night.
Humanity has marked the moment for at least five thousand years. Stonehenge’s axis frames the midsummer sunrise; Ireland’s Newgrange, older than the pyramids, channels the midwinter dawn down a stone passage to light its inner chamber for a few minutes a year. Midsummer remains a major holiday across Scandinavia, while festivals of light from Yule to Dongzhi cluster around the December date, celebrating the sun’s turnaround.
Two solstice surprises catch people out. The earliest sunset does not fall on the shortest day: at mid-northern latitudes it arrives in early December, with the latest sunrise in early January, because clock time and sun time drift apart through the “equation of time.” And the solstices are not the temperature extremes — oceans and land take weeks to heat and cool, so the hottest and coldest weather lags a month or more behind the astronomical turning point.
Nor is the solstice fixed to one date: it wanders between the 20th and 22nd as calendar years and leap days shuffle around the true 365.24-day orbit.
The exact dates of the coming solstices — and the sunrise and sunset they produce for your own city — are computed live in the sun times panel at itsdately.com.
The festivals of the December turning point circle the globe. Iran keeps Yalda, staying awake through the year’s longest night with pomegranates, poetry, and family until the reborn sun rises; China marks Dongzhi with dumplings and tangyuan as yang begins its return; and in the tropics a different spectacle bookends the year — cities between the tropics, like Honolulu, experience “zero shadow” days when the sun passes exactly overhead and vertical poles cast nothing at all, a phenomenon Hawaiians call Lahaina Noon.
The solstices also frame the year’s astronomical bookkeeping. Because our calendar year runs slightly shorter than the true orbit until a leap day repays the debt, each solstice drifts about six hours later annually, then snaps back — which is why the “longest day” can fall on the 20th, 21st, or 22nd depending on the year and your time zone. The moment itself is global and simultaneous: when the June solstice occurs, it is the same instant in Tokyo and Toronto, merely stamped with different local clocks — a yearly reminder that the seasons belong to the planet, not the calendar.
Frequently asked questions
Related on itsdately: How Long Is a Day on Other Planets? · Why Are There 60 Seconds in a Minute? Blame Babylon · What Is an Equinox? The Two Days the Sun Crosses the Equator
Further reading: U.S. Naval Observatory Astronomical Applications