Summer Solstice Day

What the summer solstice tool does

The summer solstice is the longest day of the year and the astronomical start of summer. This tool gives you its date for any year from 1900 to 2050, for either hemisphere. Pick the year and the hemisphere and it returns the day, taken from accurate astronomical data rather than a rough rule.

How to use it

1. Year. Any year from 1900 to 2050.
2. Hemisphere. Northern or Southern, since summer falls at opposite times in each.

Press Find Solstice and the date appears.

What a solstice is

Where an equinox is about balance, a solstice is about an extreme. The Earth is tilted on its axis by about 23.5 degrees, and the summer solstice is the moment that tilt leans your hemisphere as far toward the sun as it ever does. The sun climbs to its highest point in the sky, stands directly over the Tropic of Cancer at 23.5 degrees north, and gives you the most daylight of any day in the year. The word itself hints at this: it comes from Latin for "sun standing still," because around the solstice the sun's noon height barely changes from day to day before it starts to drop again.

June in the north, December in the south

The hemispheres have opposite summers, which is why the tool asks which one you want. When the northern hemisphere tips toward the sun in June for its longest day, the southern hemisphere is tilted away and having its shortest, the depth of its winter. Six months later the roles swap. So the summer solstice falls in June for the northern hemisphere and in December for the southern. If you are in the south, your longest day and the start of your summer is the December date, not the June one.

Example dates

For the northern hemisphere, the summer solstice falls on 21 June 2025 and 21 June 2026. For the southern hemisphere, summer's solstice lands on 21 December 2025 and 21 December 2026. The solstice is a single worldwide instant given in universal time, so a date near midnight can fall a day earlier or later once converted to your local time zone.

The longest day is not the earliest sunrise

Here is a detail that surprises people. You might assume the longest day also has the earliest sunrise and the latest sunset, but it does not quite work that way. Around the June solstice in the northern hemisphere, the earliest sunrise actually happens a week or so before the solstice, around the 14th, and the latest sunset a week or so after, near the 28th. The solstice has the most daylight overall, the longest gap from sunrise to sunset, but the individual earliest and latest moments sit on either side of it. It is a quirk of how the sun's timing shifts through the year, and a nice thing to know if you are chasing a particular sunrise.

Questions people ask

What date is the summer solstice?

In the northern hemisphere it falls around 20 or 21 June, and in the southern hemisphere summer's solstice is around 21 or 22 December. Choose the year and hemisphere for the exact day.

Is the summer solstice really the longest day?

Yes, it has the most daylight of any day in the year for your hemisphere, because the sun reaches its highest point and stays above the horizon longest.

Why is it June in some places and December in others?

Because the hemispheres have opposite seasons. The northern summer solstice is in June, when the south is in midwinter, and the southern summer solstice is in December.

Is the earliest sunrise on the solstice?

No. The earliest sunrise comes a little before the solstice and the latest sunset a little after, even though the solstice itself has the most daylight overall.

References

1. U.S. Naval Observatory, Astronomical Applications Department: Earth's Seasons, Equinoxes, Solstices, Perihelion, and Aphelion. https://aa.usno.navy.mil/data/Earth_Seasons