Season start calculator

When does spring start in 2026?

The March equinox, the astronomical start of spring in the Northern Hemisphere, is at Mar 20, 2026, 2:45 PM UTC and Mar 20, 2026, 10:45 AM EDT in New York, Mar 20, 2026, 7:45 AM PDT in Los Angeles. The dates of the four season starts in 2026 are March equinox Mar 20, June solstice Jun 21, September equinox Sep 23, December solstice Dec 21 (UTC).

Why is the date sometimes March 19, 20 or 21?

The tropical year is about 365.24 days, so the moment shifts by almost six hours each year and snaps back by a day in leap years. The Gregorian calendar keeps it within a narrow band, but depending on the time zone the date can differ. In 2024 the March equinox came at Mar 20, 2024, 3:07 AM UTC, which was Mar 19, 2024, 11:07 PM EDT in New York: spring began on March 19 in every US time zone and on March 20 in UTC.

What is the difference between astronomical and meteorological seasons?

Astronomical seasons begin at the equinoxes and solstices, which depend on the position of Earth relative to the Sun. Meteorological seasons are groups of whole calendar months based on the annual temperature cycle: spring is March, April and May, summer June to August, fall September to November and winter December to February in the Northern Hemisphere (NOAA NCEI). They start on the 1st of the month so that climate statistics compare cleanly.

Are the four seasons the same length?

No. Earth's orbit is an ellipse and the planet moves faster when it is closer to the Sun, near perihelion in early January. In 2026 spring lasts 92.74 days, summer 93.65, fall 89.86 and winter 88.98; summer is the longest and winter the shortest. NOAA gives the range as 89 to 93 days. Spring and summer together last 186.39 days, fall and winter 178.85, which is why the Northern Hemisphere summer half of the year is a few days longer than the winter half.

What is an equinox and what is a solstice?

At an equinox the Sun's apparent position along the ecliptic is at longitude 0° (March) or 180° (September), where the ecliptic crosses the celestial equator, and day and night are nearly equal everywhere. At a solstice the longitude is 90° (June) or 270° (December): the Sun is farthest north or south, giving the longest and shortest daylight. The calculator finds the instant when the Sun's apparent geocentric longitude reaches these values.

Does the Southern Hemisphere have the same dates?

The same moments, but with the seasons swapped: the March equinox starts fall and the September equinox starts spring in Australia, South Africa, Argentina and elsewhere south of the equator. Use the hemisphere option to relabel the seasons.

When are Earth's closest and farthest points from the Sun?

They are not season starts. The US Naval Observatory lists perihelion at January 3, 2026, 17:15 UT and aphelion at July 6, 2026, 17:30 UT. The calculator does not compute them; take the values from the Observatory's table.

How the calculation works

The method is Jean Meeus's, from chapter 27 of Astronomical Algorithms. A fourth-degree polynomial in Y = (year − 2000) ÷ 1000 gives the mean Julian Ephemeris Day of the event for each of the four moments. A correction sums 24 periodic terms of the form A × cos(B + C × T), where T counts Julian centuries from the year 2000; that sum S, divided by 1 + 0.0334 × cos W + 0.0007 × cos 2W (W = 35,999.373 T − 2.47 degrees) and multiplied by 0.00001, is added to the day number. The result is in dynamical time (TT); to get UTC the calculator subtracts ΔT, the difference between TT and universal time (about 75 seconds in 2026 on the NASA polynomial; it is predicted, not measured, for the future). The conversion to the chosen time zone uses the browser's own time zone data.

Worked example: spring 2026 in New York

For 2026 the mean polynomial plus the correction put the March equinox at Mar 20, 2026, 2:45 PM UTC. That is Mar 20, 2026, 10:45 AM EDT, since New York is on daylight time (UTC−4) from March 8. Spring then lasts until the June solstice at Jun 21, 2026, 8:25 AM UTC: 92.74 days. The US Naval Observatory's table gives the same four moments within a minute.

Accuracy and limits

We compared the calculator with the US Naval Observatory's published times for 1990, 2000, 2010, 2020–2030 and 2040; most of the 60 moments agree to the minute and none differs by more than one minute, the resolution of the Observatory's table. Meeus's Table 27.A is valid for the years 1000–3000, and the ΔT used for future years is an estimate, so the calculator is limited to 1900–2099. It gives astronomical seasons, not the dates a country, school or calendar chooses to use, and it does not account for the length of the day or the time of sunrise: for those, see the sunrise and sunset calculator. The browser applies the time zone rules in force at the date shown.

Sources: Jean Meeus, Astronomical Algorithms (Willmann-Bell, 2nd ed., 1998), chapter 27, Table 27.A and 27.C (formulas implemented independently; the book is not reproduced); Fred Espenak and Jean Meeus, polynomial expressions for ΔT, NASA Eclipse Web Site (eclipse.gsfc.nasa.gov/SEhelp/deltatpoly2004.html); US Naval Observatory, Earth's Seasons data (aa.usno.navy.mil/data/api, read October 28, 2026); NOAA National Centers for Environmental Information, “Meteorological Versus Astronomical Seasons.” Related: sunrise and sunset calculator, sun angle calculator, daylight saving time calculator, moon phase calculator and Easter date calculator.