Solstice & Equinox Dates
Find the exact dates of every solstice and equinox for any year.
The solstices and equinoxes are the four key astronomical events that mark the changing of the seasons. Twice a year, at the equinoxes, the Sun crosses the celestial equator and day and night are approximately equal in length across the globe. Twice more, at the solstices, the Sun reaches its highest or lowest point in the sky, producing the longest and shortest days of the year. These events have been observed and celebrated by civilisations for thousands of years — from Stonehenge in England to the Mayan pyramids in Mexico — and they continue to shape everything from agriculture and energy planning to cultural festivals and religious observances.
Our free solstice and equinox calculator shows you the exact dates for any year from 2020 to 2030, with hardcoded astronomical data for 2025 and 2026 and reliable approximations for other years. Each event is displayed with its date, a countdown to the next occurrence, a brief description of what happens astronomically, and approximate day-length information for London, UK. Whether you want to know when the longest day falls this year, plan a summer solstice celebration, or simply understand the rhythm of the seasons, this tool gives you all the key dates at a glance.
Day Length in London (UK) at Each Solstice
Understanding Solstices and Equinoxes
The four seasonal markers — two solstices and two equinoxes — are determined by the relationship between Earth's tilted axis and its position in orbit around the Sun. Earth's axis is tilted at approximately 23.44 degrees relative to the plane of its orbit. As Earth travels around the Sun over the course of a year, this tilt causes different parts of the planet to receive varying amounts of sunlight. The result is the seasons we experience: spring, summer, autumn, and winter. Understanding when these transitions occur helps with everything from gardening and farming to energy forecasting and holiday planning.
How to Use This Tool
- Select a year — use the dropdown to choose any year from 2020 to 2030. The current year is selected by default.
- View the seasonal grid — four cards appear showing the Spring Equinox, Summer Solstice, Autumn Equinox, and Winter Solstice with their exact dates for the selected year.
- Check the countdown — the tool highlights the next upcoming seasonal event and shows a countdown in days.
- Review day lengths — below the grid, approximate daylight hours for London at each solstice are displayed, showing the contrast between the longest and shortest days.
How It Works — Earth's Axial Tilt
Earth's rotational axis is not perpendicular to its orbital plane — it is tilted at about 23.44 degrees. This tilt is the fundamental cause of seasons. At the summer solstice (around June 21 in the Northern Hemisphere), the North Pole is tilted most directly toward the Sun, producing the longest day and shortest night. Six months later at the winter solstice (around December 21), the North Pole is tilted furthest from the Sun, resulting in the shortest day and longest night. At the two equinoxes (around March 20 and September 22-23), the tilt is oriented neither toward nor away from the Sun, and day and night are approximately equal everywhere on Earth.
The exact dates shift slightly from year to year because Earth's orbital period is approximately 365.2422 days, not exactly 365. Leap years help correct this drift, but the astronomical events still vary by a day or two. For 2025 and 2026, this tool uses precise astronomical data. For other years in the 2020-2030 range, it uses well-established approximation algorithms that are accurate to within one day.
Frequently Asked Questions
When are the 2026 solstice and equinox dates?
In 2026, the four seasonal events fall on the following dates (Northern Hemisphere): Spring Equinox on 20 March, Summer Solstice on 21 June, Autumn Equinox on 23 September, and Winter Solstice on 22 December. In the Southern Hemisphere, the seasons are reversed — the March equinox marks autumn and the September equinox marks spring.
What is the difference between a solstice and an equinox?
A solstice occurs when the Sun reaches its maximum or minimum angular distance from the celestial equator. The summer solstice is the longest day of the year (most daylight hours) and the winter solstice is the shortest day. An equinox occurs when the Sun crosses the celestial equator, making the length of day and night approximately equal everywhere on Earth. There are two solstices (June and December) and two equinoxes (March and September) each year.
When is the longest day of the year in the UK?
The longest day of the year in the UK is the summer solstice, which typically falls on 20 or 21 June. On this day, London experiences approximately 16 hours and 38 minutes of daylight, with the Sun rising around 4:43 AM and setting around 9:21 PM. Further north in Scotland, daylight can exceed 18 hours, and in Shetland it barely gets dark at all.
When is the shortest day of the year?
The shortest day of the year in the Northern Hemisphere is the winter solstice, which falls on 21 or 22 December. In London, daylight lasts only about 7 hours and 50 minutes on this day. The Sun rises around 8:04 AM and sets around 3:53 PM. After the winter solstice, days begin to lengthen again as the Northern Hemisphere gradually tilts back toward the Sun.
Do the dates fall on the same day every year?
No, the exact dates of solstices and equinoxes vary by 1 to 2 days from year to year. This is because Earth's orbital period is approximately 365.2422 days, not exactly 365. The calendar year of 365 days (or 366 in leap years) does not perfectly match the astronomical cycle, causing the dates to shift slightly. However, they always fall within a narrow window: the spring equinox between March 19-21, summer solstice between June 20-22, autumn equinox between September 22-24, and winter solstice between December 20-23.
Why do we have seasons?
Seasons are caused by Earth's axial tilt of approximately 23.44 degrees. As Earth orbits the Sun, the tilt causes different hemispheres to receive more or less direct sunlight at different times of the year. When the Northern Hemisphere is tilted toward the Sun, it receives more direct sunlight and experiences summer, while the Southern Hemisphere is tilted away and experiences winter. Six months later, the situation reverses. Without the axial tilt, there would be no seasons — every day would have roughly the same amount of daylight everywhere on Earth.
