Equinoxes and Solstices: Dates, Times and Why They Shift

An equinox or solstice is a single moment, not a whole day. The two equinoxes, in March and September, are the instants when the Sun crosses directly over the equator. The two solstices, in June and December, are the instants when it reaches its farthest point north or south. Their calendar dates move between the 19th and the 23rd of the month depending on the year and the time zone.

The table below this guide lists every equinox and solstice from 2020 to 2030 with dates and times in US Eastern Time. The sections here explain what the four events are, why they wander on the calendar and what they mean for daylight in different parts of the country.

What equinoxes and solstices are

Earth’s axis is tilted about 23.5 degrees, and the tilt keeps pointing the same direction in space as Earth circles the Sun. In June the Northern Hemisphere leans toward the Sun; in December it leans away. That tilt, not Earth’s changing distance from the Sun, causes the seasons. Earth is actually closest to the Sun in the first week of January.

The four events mark the turning points:

• March equinox. The Sun crosses the equator heading north. Astronomical spring begins in the Northern Hemisphere.
• June solstice. The Sun stands directly over the Tropic of Cancer, about 23.5 degrees north. Summer begins, and US locations get their longest daylight of the year.
• September equinox. The Sun crosses the equator heading south. Fall begins.
• December solstice. The Sun stands over the Tropic of Capricorn. Winter begins, with the shortest daylight and longest night.

The word equinox comes from Latin for “equal night.” The name is close but not exact, as the daylight section below shows. Solstice comes from Latin words meaning that the Sun “stands still,” because its noon height stops climbing or falling for a few days around these dates. The seasons are reversed in the Southern Hemisphere, but the moments are the same worldwide.

Why the dates shift between the 19th and 23rd

Two things move these events around the calendar: the leap-year cycle and time zones.

The leap-year cycle

Earth takes about 365.2422 days to complete one cycle of the seasons, a period called the tropical year. A common calendar year has only 365 days, so each event comes about 0.2422 days later on the clock each year. That is 0.2422 × 24 = 5.8 hours, or about 5 hours and 49 minutes. Every fourth year, February 29 pulls the date back by a full day.

The March equinox shows the pattern in Universal Time:

Year	March equinox (UT)	Change from previous year
2025	March 20, 09:01
2026	March 20, 14:46	5 h 45 min later
2027	March 20, 20:25	5 h 39 min later
2028	March 20, 02:17	about 18 h earlier on the clock, after February 29

The yearly step is not exactly 5 hours 49 minutes because the Moon and planets nudge Earth slightly, which moves each event by a few minutes either way.

The leap-day correction also overshoots a little. Four calendar years hold 1,461 days, while four seasonal years take about 4 × 365.2422 = 1,460.97 days. The calendar runs about 0.03 day, or roughly 45 minutes, long every four years, so the equinox creeps earlier through a century. That is why the March equinox will fall on March 19 in Universal Time in 2096. Skipping the leap day in 2100, under the century rule explained in our leap years guide, will push it back later again.

Time zones

An equinox at 2:00 a.m. Universal Time is still the evening before in the United States. In 2024 the March equinox came at 03:06 UT on March 20, which was 11:06 p.m. EDT on March 19. Spring began on March 19 in every US time zone that year, even though calendars printed in Europe show March 20. The 2024 calendar marks it on the 19th for that reason. Our guide to time zones in the United States covers more of these date shifts.

In Eastern Time, from 1990 through 2099, the March equinox falls on March 19 or 20, the June solstice on June 20 or 21, the September equinox on September 21, 22 or 23, and the December solstice on December 20, 21 or 22.

The four seasons are not the same length

Earth’s orbit is slightly elliptical, and Earth moves fastest when it is closest to the Sun in early January. The Northern Hemisphere winter is therefore the shortest astronomical season and summer the longest. NOAA’s climate center notes that astronomical seasons range from about 89 to 93 days.

Here is the arithmetic for the seasons that began in 2026, using Universal Time:

• Spring: March 20, 14:46 to June 21, 08:25 = 92 days, 17 hours, 39 minutes
• Summer: June 21, 08:25 to September 23, 00:06 = 93 days, 15 hours, 41 minutes
• Fall: September 23, 00:06 to December 21, 20:50 = 89 days, 20 hours, 44 minutes
• Winter: December 21, 20:50 to March 20, 2027, 20:25 = 88 days, 23 hours, 35 minutes

Northern summer runs about four and a half days longer than northern winter. The four add up to 365.24 days.

Astronomical seasons vs meteorological seasons

Because astronomical seasons start on different dates and run different lengths, they make poor buckets for climate statistics. Climatologists use meteorological seasons instead, built from whole calendar months grouped by temperature:

• Spring: March, April and May
• Summer: June, July and August
• Fall: September, October and November
• Winter: December, January and February

Meteorological seasons line up with monthly weather records, so it is easy to compare one summer with another. They also match how most of the country feels. The National Weather Service office in Cleveland notes that the warmest part of summer in northern Ohio and northwest Pennsylvania arrives nearly three weeks after the June solstice, because land and water keep warming after the longest day has passed.

In practice, a weather report that calls September 1 the start of fall and a calendar that shows fall beginning on September 22 or 23 are both correct. They use different systems.

How daylight changes across the United States

Latitude decides how much the daylight swings between summer and winter. The figures below are calculated from each city’s latitude with the standard sunrise and sunset formula, which counts refraction and the top edge of the Sun. They are rounded and will differ from a local almanac by a minute or two.

City	Approx. latitude	June solstice	Equinox	December solstice
Honolulu	21° N	13 h 26 min	12 h 7 min	10 h 50 min
Miami	26° N	13 h 45 min	12 h 7 min	10 h 32 min
Los Angeles	34° N	14 h 25 min	12 h 8 min	9 h 53 min
Washington, DC	39° N	14 h 54 min	12 h 9 min	9 h 26 min
Seattle	48° N	15 h 59 min	12 h 10 min	8 h 25 min
Anchorage	61° N	19 h 22 min	12 h 14 min	5 h 27 min

Two patterns stand out. First, the yearly swing grows quickly with latitude: about 2.5 hours in Honolulu, about 7.5 in Seattle and almost 14 in Anchorage. In Alaska’s far north, above the Arctic Circle, the Sun stays up around the clock for a stretch of early summer and stays below the horizon for a stretch around the December solstice.

Second, every city gets slightly more than 12 hours of daylight on the equinox. The National Weather Service attributes this mostly to refraction, which bends sunlight over the horizon so the Sun appears before it has truly risen and lingers after it has set. As a result, the day with equal daylight and darkness comes a few days before the March equinox and a few days after the September one.

Earliest sunset and latest sunrise

The December solstice is the shortest day, but it is not the day with the earliest sunset. Through December, solar noon drifts later on the clock, a combination of Earth’s tilt and its faster orbital motion as it nears its January closest approach to the Sun. Sunrise and sunset both slide later along with it, so the evening gains light while the morning keeps losing it.

In most of the lower 48 states, the result is that the earliest sunsets come in early to mid-December and the latest sunrises come in early January. For a commuter in Washington, DC, the evenings start getting lighter in the second week of December, while the mornings keep getting darker until the first week of January.

Equinoxes and solstices on the holiday calendar

Several dates on Old Calendars depend on these events or sit near them:

• The Harvest Moon is the full moon closest to the September equinox, so it can fall in September or early October. See moon phases explained.
• Easter uses a fixed ecclesiastical equinox of March 21 rather than the astronomical moment. The details are in how Easter’s date is calculated.
• Groundhog Day on February 2 sits roughly midway between the December solstice and the March equinox: about 43 days after one and 46 days before the other in a typical year.

Each year calendar on this site marks the four events with their Eastern Time dates. The 2026 calendar shows the September equinox on September 22 at 8:05 p.m. EDT, even though the same moment was already September 23 in Universal Time.