Changing when the Seasons Start...

1st Question: When do the seasons began?
2nd Question: Are there different ways to define seasons?
3rd Question: How about a more psychologically appealing seasons?

There are four main dates in the calendar that relate to the environment we live in: the December and June solstices, and the March and September equinoxes. Seasons have been defined by certain periods of time in a year. Seasons usually indicate changes in amount of daylight and the weather. But there are regions of the world where the daylight does not change much during the year but the weather can: e.g. monsoon season or rainy season. But we'll stick with the typical temperate zone seasons of spring, summer, fall, and winter.

Popular media will use those dates to indicate when a season "starts" as in winter starts on December 21 or 22 in the northern hemisphere. But seasons can be defined in different ways.

An astronomical POV could be used where it is the position of the sun in the sky that determines the seasons. In this case, solstices and equinoxes would be the middle of the seasons. For example, the June solstice is the day the sunrises the earliest and should be in the middle of northern hemisphere summer (not the start). Therefore, astronomical seasons start in between a solstice and equinox. Some call these dates cross-quarter days, or days halfway between a solstice and equinox. In the northern hemisphere, this would be on Feb 1 or 2, May 1, Aug 1-2, and Oct 31-Nov 1. This is similar to using the amount of sunlight received (insolation) to determine various quarters of the year.

Another way to look at when the seasons start is based upon the weather (or temperature). When using average temperatures for a particular hemisphere, the starts of the seasons are March 1, June 1, September 1, and December 1. In general, the temperature changes typical for those seasons have not started at these dates (possibly due to so called thermal lag).

So where does that leave us?

	Spring	Summer	Fall	Winter
Astronomic	February 1,2	May 1	August 1,2	October 31,November 1
Meteorologic	March 1	June 1	September 1	November 1
Popular Media	March 20,21	June 20,21	September 22,23	December 21,22

Can we improve upon these definitions?

Why not take the sunlight approach but disregard the need to have seasons with similar number of days. Using Chicago as an example, below is a graph of the sunrise and sunset times:

The amount of daylight varies from 9:08 to 15:14 throughout the year. We can divide the amount of possible daylight per day into 4 equal durations:

• 9:08 to 10:39:30
• 10:39:30 to 12:11
• 12:11 to 13:42:30
• 13:42:30 to 15:14

There will be 2   periods of the year where each of these durations would occur. Therefore, we could define winter as the 2 sections with the least daylight while summer would be the 2 sections with the most daylight. Spring and Fall would occur in between. If we do that, what do the seasons look like?

So spring is from February 16 to April 22. Summer goes until August 18. Fall ends at October 24. Winter continues through February 16. 

• Spring: February 16 to April 22
• Summer: April 23 to August 18
• Fall: August 19 to October 24
• Winter: October 25 to February 15

The solstices and equinoxes are in the middle of their respective seasons. But the length of each season is different: Summer and winter are about 16 1/2 weeks each. Spring and fall are about 9 1/2 weeks each. 

But there is another way to define a season: using the sunset (or sunrise). Excluding daylight savings, sunset varies from 16:19 to 19:30. Like the hours of daylight, you can divide that up into quarters and assign seasons based upon what range of sunset times occur.  

Using that idea, spring would start on February 2. Summer starts on April 24. Fall starts on August 20. And winter begins on October 16. 

• Spring: February 2 to April 23
• Summer: April 24 to August 19
• Fall: August 20 to October 15
• Winter: October 16 to February 1

But if you add daylight savings and assume the latest sunset is at 20:30, things are little more interesting. Spring would start on February 9. Summer begins on April 11. Fall starts on August 30. And winter begins on November 4. So where does that leave us?

	Spring	Summer	Fall	Winter
Astronomic	February 1,2	May 1	August 1,2	October 31,November 1
Meteorologic	March 1	June 1	September 1	November 1
Popular Media	March 20,21	June 20,21	September 22,23	December 21,22
Daylight Duration	February 16	April 22,23	August 18	October 24,25
Sunset	February 2	April 24	August 20	October 16
Sunset w/ Daylight Savings	February 9,10	April 11	August 30	November 4

Anyway, that's just me. So what do we use? The best combination of seasons would be the one with long summers, not as long winters, and spring happening earlier. And using the sunset times with daylight savings fits those requirements: Spring starts 6 weeks early. Summer is 20 weeks long. Winter starts earlier but only lasts 14 weeks. Maybe this should be called the socioeconomic seasons? Just a thought.