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About the Seasons Calculator

The Seasons Calculator calculates the time and date of the March equinox, the June solstice, the September equinox and the December solstice at a chosen location. These dates mark the beginning of the four seasons of the year: spring, summer, autumn (or fall) and winter.

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©iStockphoto.com/joaquin croxatto

The Seasons Calculator Explained

The Seasons Calculator calculates the equinoxes and solstices for years as far back as 1 and up to the year 2099.

Simply select any location that is available in the World Clock and the calculator will adjust to the local time in that particular city. If the location is not specified, the times will be based on Coordinated Universal Time (UTC) or Greenwich Mean Time (GMT).The times shown will reflect any daylight saving observations in a selected location.

The dates shown for the calculations are primarily based on the Gregorian calendar. However, the Julian calendar is used to calculate dates that pre-date the Gregorian calendar, which was first introduced in 1582.

Seasons in the southern hemisphere are opposite to those in the northern hemisphere. For example, the March equinox, also popularly known as the vernal equinox in the northern hemisphere, marks the start of spring in the northern hemisphere but the start of autumn in the southern hemisphere. The same rule applies for the other three seasons.

March Equinox

The March equinox occurs when the sun crosses the true celestial equator – or the imaginary line in the sky above the Earth’s equator – from south to north on a day between March 20 and 23. In other words, the sun moves north of the equator during the March equinox.

During the March equinox, the length of day is about 12 hours and eight to nine minutes in areas that are about 30 degrees north or south of the equator, while areas that are 60 degrees north or south of the equator receive daylight for about 12 hours and 16 minutes. Regions around the equator have a daylight period of about 12 hours and six-and-a-half minutes during the March equinox.

The March equinox is an important event in many calendars, as it coincides with a variety of cultural events, religious observances or customs. Read more about the March equinox and holidays, observances and customs that occur during this time of the year.

June Solstice

The June solstice is also referred to as the summer solstice in the northern hemisphere and the winter solstice in the southern hemisphere. This is the time when the sun is at its furthest point from the equator – it reaches its northernmost point on a day between June 20 and 22, and the Earth’s north pole tilts towards the sun.

The June solstice is also known as the northern solstice because it occurs when the sun is directly over the Tropic of Cancer in the northern hemisphere. This is the longest day for those living north of this latitude. North of the Arctic Circle the "midnight sun" can be observed, while locations south of the Antarctic Circle do not receive any direct sunlight. Read more about the June solstice and customs and traditions associated with this event.

September Equinox

The September equinox is also referred to as the autumnal, autumn or fall equinox in the northern hemisphere. It is known as the spring or vernal equinox in the southern hemisphere as countries including South Africa and Australia enter the spring season. It occurs on a day between September 21 and 24 when the Earth’s axis of rotation is perpendicular to the imaginary line connecting the centers of the Earth and the sun.

During the September equinox the sun crosses the celestial equator and moves southward. At this point in time, regions around the equator have a daylight length of about 12 hours and six-and-a-half minutes. Read more about the September equinox and customs and holidays associated with this event.

December Solstice

The December solstice is also called the winter solstice in the northern hemisphere and the summer solstice in the southern hemisphere. It occurs on a day between December 20 and 23. At this point the sun appears directly above the Tropic of Capricorn, and the days are shortest at locations north of the Tropic of Cancer. South of the Antarctic Circle the sun is now visible 24 hours per day. Read more about the December solstice and customs and traditions relating to the event.

Local Time Conversion

The seasons calculator automatically takes into account daylight saving time at the selected location, except for UTC/GMT. To display the seasons for a location within this timezone (e.g. London) please select the city - not UTC/GMT. If you select a future year, the results may be wrong due to future changes in a country's daylight saving time rules. For years before the introduction of standard time zones, the calculator may display "local mean solar time", which is an average yearly value based on the moment when the sun passes a location's meridian. In reality, this moment may differ by up to 17 minutes from the average passing time.

Calendar Change

For many countries, but not all, the change from the Julian to the Gregorian calendar will be visible as about 10-13 days are missing in the respective year. In many countries that did not use the Julian calendar or the Gregorian calendar until recently, the Gregorian calendar is used for all years after 1582 (when the Gregorian calendar was first adopted in some European countries). For years before 1582 the Julian calendar is used. Although in many regions the calendar year did not always begin on January 1, this calculator always displays January 1 as the first day of the year for the sake of simplicity.

Calculation Accuracy

For years between 1700 and 2100, the accuracy of the times calculated should be within one minute of the real time. For years before 1700, accuracy will be less as we calculate back in time.


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