Solstices and Equinoxes

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The equinoxes, solstices and seasons only exist because the axis of rotation of the Earth is at an angle of 23.4 degrees, to the vertical with respect to the plane (the ecliptic) formed by the revolution of the Earth about the Sun.

Because the Earth's axis is directed at the same point in space as it revolves around the Sun, the angle of tilt of the axis with respect to the Sun varies, from a minimum of 0 degrees (which defines the equinoxes) to a maximum of 23.4 degrees toward or away (which defines the summer and winter solstices, respectively).

Southern Hemisphere

 

Northern Hemisphere

Angle from perpendicular to ecliptic

Angle from perpendicular to ecliptic

The change in angle between the southern end of the Earth's axis and the ecliptic for 1 year (ie. 1 revolution).
Positive values indicate tilt toward the Sun.

 

The change in angle between the northern end of the Earth's axis and the ecliptic for 1 year (ie. 1 revolution).
Positive values indicate tilt toward the Sun.

The subsolar point is the point on the Earth's surface where the Sun's radiation strikes at a 90 degree angle; alternatively it is the point on the Earth where the Sun is directly overhead at noon.

June Solstice

Equinoxes

December Solstice

Subsolar point

Tropic of Cancer

Equator

Tropic of Capricorn

23.4 degrees N

0 degrees

23.4 degrees S

Because the Earth's orbit is slightly elliptical, there is a point on the orbit where the Earth is further away from the Sun than at any other time (Aphelion, ~July 4) and a point approximately opposite on the orbit where the Earth is closer to the Sun than at any other time (Perihelion, ~Jan 3).

Revolution of Earth about Sun

The times for equinoxes and solstices (as well as aphelion & perihelion) are shown on the U.S. Navy web site , for Greenwich, England.  An explanation of Universal Time (UT), which approximates to Greenwich Mean Time (GMT), is given on the same site.

Melbourne, Australia:

Longitude:  145° 08' East

Event

September Equinox
Sat, 23 Sep 2017, 6:02 AM AEST
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GMT values have been converted to Australian Eastern Standard Time (GMT + 10), and are shown below:
Note: Add 1 hour to obtain correct local times for the December Solstice and March Equinox for the states in Australia that change to Australian Eastern Daylight Time during the warmer months.

March Equinox
Autumn

June Solstice
Winter

September Equinox
Spring

December Solstice
Summer

2001

Mar 20

23:31

Jun 21

17:38

Sep 23

9:04

Dec 22

5:21

 

2002

Mar 21

5:16

Jun 21

23:24

Sep 23

14:55

Dec 22

11:14

 

2003

Mar 21

11:00

Jun 22

5:10

Sep 23

20:47

Dec 22

17:04

 

2004

Mar 20

16:49

Jun 21

10:57

Sep 23

2:30

Dec 21

22:42

 

2005

Mar 20

22:33

Jun 21

16:46

Sep 23

8:23

Dec 22

4:35

 

2006

Mar 21

4:26

Jun 21

22:26

Sep 23

14:03

Dec 22

10:22

 

2007

Mar 21

10:07

Jun 22

4:06

Sep 23

19:51

Dec 22

16:08

 

2008

Mar 20

15:48

Jun 21

9:59

Sep 23

1:44

Dec 21

22:04

 

2009

Mar 20

21:44

Jun 21

15:45

Sep 23

7:18

Dec 22

3:47

 

2010

Mar 21

3:32

Jun 21

21:28

Sep 23

13:09

Dec 22

9:38

 

2011

Mar 21

9:21

Jun 22

3:16

Sep 23

19:05

Dec 22

15:30

 

2012

Mar 20

15:14

Jun 21

9:09

Sep 23

0:49

Dec 21

21:12

 

2013

Mar 20

21:02

Jun 21

15:04

Sep 23

6:44

Dec 22

3:11

 

2014

Mar 21

2:57

Jun 21

20:51

Sep 23

12:29

Dec 22

9:03

 

2015

Mar 21

8:45

Jun 22

2:38

Sep 23

18:20

Dec 22

14:48

 

2016

Mar 20

14:30

Jun 21

8:34

Sep 23

0:21

Dec 21

20:44

 

2017

Mar 20

20:28

Jun 21

14:24

Sep 23

6:02

Dec 22

2:28

 

2018

Mar 21

2:15

Jun 21

20:07

Sep 23

11:54

Dec 22

8:22

 

2019

Mar 21

7:58

Jun 22

1:54

Sep 23

17:50

Dec 22

14:19

 

2020

Mar 20

13:49

Jun 21

7:43

Sep 22

23:30

Dec 21

20:02

 

Number of times for a particular date:
   

Mar 20

10

 

Jun 21

15

 

Sep 22

1

 

Dec 21

5

 

 

 

Mar 21

10

 

Jun 22

5

 

Sep 23

19

 

Dec 22

15

 

A better idea of the relative frequencies for particular Melbourne dates over a 142 year period are shown here.

Toronto, Canada:

Longitude:  79° 22' West

Event

September Equinox
Fri, 22 Sep 2017, 4:02 PM EDT
top

GMT values have been converted to Eastern Standard Time (GMT - 5), and are shown below:
Note: Add 1 hour to obtain correct local times for the March Equinox, June Solstice and September Equinox for the areas that change to Eastern Daylight Time during the warmer months.

March Equinox
Spring

June Solstice
Summer

September Equinox
Autumn

December Solstice
Winter

2001

 

Mar 20

8:31

 

Jun 21

2:38

 

Sep 22

18:04

 

Dec 21

14:21

 

2002

 

Mar 20

14:16

 

Jun 21

8:24

 

Sep 22

23:55

 

Dec 21

20:14

 

2003

 

Mar 20

20:00

 

Jun 21

14:10

 

Sep 23

5:47

 

Dec 22

2:04

 

2004

 

Mar 20

1:49

 

Jun 20

19:57

 

Sep 22

11:30

 

Dec 21

7:42

 

2005

 

Mar 20

7:33

 

Jun 21

1:46

 

Sep 22

17:23

 

Dec 21

13:35

 

2006

 

Mar 20

13:26

 

Jun 21

7:26

 

Sep 22

23:03

 

Dec 21

19:22

 

2007

 

Mar 20

19:07

 

Jun 21

13:06

 

Sep 23

4:51

 

Dec 22

1:08

 

2008

 

Mar 20

0:48

 

Jun 20

18:59

 

Sep 22

10:44

 

Dec 21

7:04

 

2009

 

Mar 20

6:44

 

Jun 21

0:45

 

Sep 22

16:18

 

Dec 21

12:47

 

2010

 

Mar 20

12:32

 

Jun 21

6:28

 

Sep 22

22:09

 

Dec 21

18:38

 

2011

 

Mar 20

18:21

 

Jun 21

12:16

 

Sep 23

4:05

 

Dec 22

0:30

 

2012

 

Mar 20

0:14

 

Jun 20

18:09

 

Sep 22

9:49

 

Dec 21

6:12

 

2013

 

Mar 20

6:02

 

Jun 21

0:04

 

Sep 22

15:44

 

Dec 21

12:11

 

2014

 

Mar 20

11:57

 

Jun 21

5:51

 

Sep 22

21:29

 

Dec 21

18:03

 

2015

 

Mar 20

17:45

 

Jun 21

11:38

 

Sep 23

3:20

 

Dec 21

23:48

 

2016

 

Mar 19

23:30

 

Jun 20

17:34

 

Sep 22

9:21

 

Dec 21

5:44

 

2017

 

Mar 20

5:28

 

Jun 20

23:24

 

Sep 22

15:02

 

Dec 21

11:28

 

2018

 

Mar 20

11:15

 

Jun 21

5:07

 

Sep 22

20:54

 

Dec 21

17:22

 

2019

 

Mar 20

16:58

 

Jun 21

10:54

 

Sep 23

2:50

 

Dec 21

23:19

 

2020

 

Mar 19

22:49

 

Jun 20

16:43

 

Sep 22

8:30

 

Dec 21

5:02

 

Number of times for a particular date:
   

Mar 19

2

 

Jun 20

6

 

Sep 22

15

 

Dec 21

17

 

 

 

Mar 20

18

 

Jun 21

14

 

Sep 23

5

 

Dec 22

3

 

A better idea of the relative frequencies for particular Toronto dates over a 142 year period are shown here.

Links to the Melbourne Planetarium:
The Path of the Sun
The Sun and the Seasons

Links to other detailed observations and explanations:
Earth at Perihelion (NASA)
Milankovitch Cycles (US Naval Observatory)
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