Science & history · Seasons and clocks
Solstices and equinoxes are moments, not days
The June solstice is the instant the Sun reaches its farthest point north; the March equinox is when it crosses the equator heading north.
The next equinox or solstice
Worked out in your browser for today's date.
One instant
Because each is a single moment, it falls on different calendar dates in different time zones. USNO lists them to the minute in Universal Time (seasons data); this site computes them itself (method) and its tests hold the results within two minutes of USNO's table in seven years between 1900 and 2050.
Hemisphere-neutral names
The June solstice begins astronomical summer in the north and winter in the south. Naming them by month avoids getting that backwards (NASA on the hemispheres).
Sources
- US Naval Observatory Astronomical Applications API (opens in a new tab) for independent sunrise, sunset, civil twilight, transit and seasons for the engine's tests · checked 2 October 2026
- Cool Moon Facts How the Sun pages calculate for the engine, its definitions, its independent checks and its limits
- NASA Space Place What Causes the Seasons? (opens in a new tab) for tilt, not distance; perihelion in January · checked 2 October 2026