16h 38m
Monday, June 21 · in 307 days
The longest day of the year — also called the summer solstice — is the day when the sun reaches its highest point in the sky and daylight lasts longer than on any other day of the year. In the Northern Hemisphere this falls around June 20 or 21. In the Southern Hemisphere the roles are reversed: June is midwinter, and the longest day falls around December 21 or 22.
The exact date shifts slightly from year to year because the solar year is about 365.25 days long — not a clean 365. Leap years pull the solstice a day earlier; the pattern then slowly drifts back.
How much daylight you get on the summer solstice depends almost entirely on your latitude. The closer you are to a pole, the more extreme the swing between your longest and shortest day. Near the equator, there is almost no difference at all.
| Location | Latitude | Day length at summer solstice |
|---|---|---|
| Tromsø, Norway | 70°N | 24 h 00 min (midnight sun — sun does not set) |
| London, UK | 51°N | ~16 h 38 min |
| New York, USA | 41°N | ~15 h 05 min |
| Singapore | 1°N | ~12 h 12 min |
| Sydney, Australia | 34°S | ~9 h 53 min (their shortest day) |
Above the Arctic Circle (66.5°N), the sun does not set at all around the solstice. This is the famous midnight sun. At the other extreme, locations above the Antarctic Circle experience polar night — continuous darkness — at this same time of year.
The word solstice comes from Latin sol (sun) + sistere (to stand still) — at this moment the sun's northward journey pauses before reversing. From the day after the summer solstice, days in the Northern Hemisphere begin to shorten again, though the change is imperceptibly slow at first: only a minute or two per day in late June and July. By the time the autumn equinox arrives in late September, the rate of shortening has accelerated to several minutes per day. The cycle ends at the winter solstice in December, when the shortest day of the year arrives.
Counterintuitively, the hottest weather of the year typically arrives after the solstice — in July and August in the Northern Hemisphere — because it takes time for the land and oceans to absorb and re-radiate the solar energy that has been building since spring.
Cultures across the world have marked the summer solstice for thousands of years. In Scandinavia, midsummer is one of the most celebrated holidays of the year — bonfires are lit, flower crowns worn, and people dance around maypoles. Stonehenge in England aligns precisely with the midsummer sunrise and has drawn visitors for this moment for over 4,000 years. In China, the summer solstice is celebrated as Xiazhi, a day associated with yin energy beginning to grow. Indigenous cultures across the Americas, from the Inca to the Lakota, built astronomical monuments oriented to solstice sunrises and sunsets.
If you are south of the equator, the June solstice is your winter solstice — your shortest day, not your longest. Your longest day falls in December. The seasons are simply mirrored: while London enjoys 16+ hours of daylight in June, Sydney gets fewer than 10.
Use the tool on the homepage to see the exact sunrise, sunset, and day length for your location today — and on any date you choose.
The word comes from the Latin sol and sistere — sun, and to stand still. It describes something you can genuinely observe: through spring the point on the horizon where the sun rises creeps steadily northwards day after day, and around the solstice it stops, hangs in place for several days, and then begins to creep back.
The solstice itself is not a day but an instant — the moment the sun reaches its greatest declination north of the celestial equator. That instant has a time as well as a date, and because it is fixed in universal time, the local calendar date can differ by a day depending on your timezone. It also drifts within the calendar, falling between 20 and 22 June, because the tropical year is not a whole number of days and the leap-year system corrects for it in jumps.
What the solstice is not is the day the Earth is closest to the sun. That happens in early January, when the northern hemisphere is in the depths of winter — a useful reminder that seasons are made by axial tilt, not by distance.
The longest day is the day with the most daylight, but it is not the day with the earliest sunrise or the latest sunset. In London the earliest sunrise falls around 17 June and the latest sunset around 24 June, with the solstice sitting between them.
The cause is the equation of time: solar noon itself drifts against clock time across the year, by up to about sixteen minutes, because the Earth's orbit is elliptical and its axis is tilted. Around the June solstice the whole solar day is shifting slightly later, which pulls the earliest sunrise forward of the solstice and pushes the latest sunset after it. Our page on when it is lightest works through the mechanism.
The headline figure — 16 hours 38 minutes in London, over 17 hours 30 minutes in Copenhagen — undersells the experience, because it counts only the time the sun is above the horizon. At these latitudes the sun sets at a shallow angle and takes a long time to get properly out of the way.
Adding civil twilight at both ends, London gets something closer to 18 hours of usable light around midsummer. Further north it goes further still: across all of Britain and Denmark the sun never reaches 18° below the horizon in late June, so astronomical darkness does not occur at all and the night is a continuous dusk running into dawn. North of the Arctic Circle the sun does not set at all. See when it gets dark for the thresholds.
The longest day is very rarely the warmest. Ground and ocean keep absorbing more heat each day than they release for weeks after the solstice, so temperatures continue climbing until the daily gain and loss balance — typically late July or early August in maritime northern Europe. This seasonal lag is why the height of summer arrives when the days are already visibly shortening, and why the first genuinely dark evening of August can feel like an ambush.
In the northern hemisphere it falls between 20 and 22 June, most often on 21 June. The date varies because the solstice is an instant fixed in universal time rather than a calendar day, and because the tropical year is not a whole number of days.
Because of the equation of time — solar noon drifts against clock time across the year by up to about sixteen minutes, since the Earth’s orbit is elliptical and its axis is tilted. In London the earliest sunrise falls around 17 June and the latest sunset around 24 June, with the solstice between them.
Because of seasonal lag. Ground and ocean keep absorbing more heat each day than they release for weeks after the solstice, so temperatures keep climbing until the daily gain and loss balance — typically late July or early August in maritime northern Europe.