In 2020, the March equinox falls on Friday, March 20, 2020 at 00:50 Brasília time, the June solstice on Saturday, June 20, 2020, the September equinox on Tuesday, September 22, 2020 and the December solstice on Monday, December 21, 2020. In Brazil these mark the start of autumn, winter, spring and summer, respectively.
2020 is already over: every event below has taken place.
Dates and times of the seasons in 2020
| Event | Date and time (Brasília, UTC-3) | UTC | Starts in Brazil | Northern hemisphere |
|---|---|---|---|---|
| March equinox | Friday, March 20, 2020, 00:50 | Mar 20, 03:50 | Autumn | Spring |
| June solstice | Saturday, June 20, 2020, 18:43 | Jun 20, 21:43 | Winter | Summer |
| September equinox | Tuesday, September 22, 2020, 10:30 | Sep 22, 13:30 | Spring | Autumn |
| December solstice | Monday, December 21, 2020, 07:02 | Dec 21, 10:02 | Summer | Winter |
Length of each season in 2020
| Season in Brazil | Northern hemisphere equivalent | Starts | Ends | Length |
|---|---|---|---|---|
| Autumn | Spring | Mar 20, 2020 | Jun 20, 2020 | 92 days 18 h |
| Winter | Summer | Jun 20, 2020 | Sep 22, 2020 | 93 days 16 h |
| Spring | Autumn | Sep 22, 2020 | Dec 21, 2020 | 89 days 21 h |
| Summer | Winter | Dec 21, 2020 | Mar 20, 2021 | 89 days |
The seasons are not equally long because the Earth's orbit is an ellipse: the planet moves faster when it is closer to the Sun (in January) and slower when it is farther away (in July). That is why winter in Brazil is the longest season and summer the shortest, while the northern hemisphere sees the opposite.
Notes on the 2020 seasons
The year 2020 is a leap year, with 366 days. Compared with the previous year, each event falls at a different time of the same calendar day:
- March equinox: 18h08min earlier than in 2019
- June solstice: 18h11min earlier than in 2019
- September equinox: 18h19min earlier than in 2019
- December solstice: 18h17min earlier than in 2019
The pattern is always the same: in common years the events slip about six hours later, and after the February 29 of a leap year they jump back by roughly 18 hours.
Seasons in each hemisphere
The seasons are opposite on either side of the equator. In Brazil and the rest of the southern hemisphere, autumn begins at the March equinox, winter at the June solstice, spring at the September equinox and summer at the December solstice. In the northern hemisphere the same four moments start spring, summer, autumn and winter. So when it is Christmas in Brazil, in the middle of summer, it is the start of winter in Europe and the United States.
Equinoxes and solstices explained
The Earth's axis is tilted about 23.4 degrees from the plane of its orbit, and this tilt, not the distance from the Sun, is what causes the seasons. At a solstice one hemisphere is leaning as far as possible toward the Sun: it gets the longest day of the year, while the other hemisphere has its shortest day. At an equinox the axis points sideways relative to the Sun, the Sun is directly above the equator, and day and night last almost exactly 12 hours everywhere on the planet. In fact the Earth is closest to the Sun in early January, which is summer in Brazil and winter in the north.
Why the dates vary between the 20th and the 23rd
A tropical year, the time to complete one cycle of seasons, lasts about 365.2422 days, while the calendar uses 365 or 366. Each common year the events slip about six hours later, and leap years pull them back. The Gregorian rule that skips leap years in century years not divisible by 400 adds a slower correction. The result is that the equinoxes and solstices wander between the 20th and the 23rd of their months. The dates also depend on the time zone: an event shortly after midnight UTC can fall on the previous evening in Brasília.
Season dates for other years
See also the Moon phase calendar, the sunrise and sunset times and the week number of the year.