Astronomical & visual time
Equinox & solstice countdown
The turning points of the year, counted to the second. See exactly how long until the next equinox and solstice — computed from the sun's declination and shown in your local time.
Instants are computed from the sun's declination and shown in your local zone. Equinoxes are the moments day and night are near-equal; solstices are the sun's highest and lowest yearly points.
How to use the equinox & solstice countdown
See the next turning point
The upcoming equinox or solstice is counted down to the second, computed as a real astronomical instant.
Read it in your zone
These are single global moments, so the local date can differ by a day between hemispheres and zones. The date shown is yours.
Look at the whole year
All four events are listed, which makes the uneven spacing between them visible.
Connect it to day length
Solstices are the longest and shortest days; equinoxes are when day and night are close to equal everywhere.
Equinoxes, solstices and why the dates move
A solstice is the instant Earth's axial tilt points most directly toward or away from the sun; an equinox is the instant the sun crosses the celestial equator. These are moments, not days — the June solstice happens at one specific second that is simultaneously an evening in Europe and a morning in Asia, which is why the calendar date differs by region.
The dates drift because the tropical year is about 365.2422 days, not 365. The extra quarter-day accumulates until a leap year absorbs it, so each event moves about six hours later per year and then jumps back. That is why the June solstice can fall on the 20th or the 21st depending on the year.
The four seasons are not equal in length. Earth's orbit is elliptical and it moves faster near perihelion in early January, so the northern winter — between the September equinox and the March one — is a few days shorter than the northern summer. Northern summer runs roughly 93.6 days and northern winter roughly 89 days.
The equinox is also not exactly equal day and night, despite the name. Sunrise is measured from the sun's upper edge and refraction lifts the disc visually, so daylight slightly exceeds twelve hours on the equinox itself. The genuinely equal day, called the equilux, falls a few days either side depending on latitude.
When you'd reach for it
Seasonal planning
Know exactly when the days start getting longer or shorter again.
Festivals and traditions
Midsummer, solstice observances and many holidays are anchored to these dates.
Photography at alignment sites
Stonehenge, Newgrange and countless other sites align to a solstice sunrise.
Teaching the seasons
A concrete countdown makes axial tilt tangible for a class.
Gardening
Planting calendars key off day length far more than off the calendar month.
Beating the winter
Counting down to the solstice is a genuinely popular way through December.
Questions & answers
- How are the dates computed?
- By tracking the sun's declination through the year: equinoxes are where it crosses the equator (0°), and solstices are its yearly extremes. The instants are accurate to within a few hours.
- Why do the times shift year to year?
- The tropical year isn't a whole number of days, so each event drifts by roughly six hours annually, corrected by leap years — which is why calendar dates wobble by a day or two.
- Are these shown in my time zone?
- Yes. The underlying instant is universal, but the date and time are formatted for your browser's local zone.