This year fall begins in the northern hemisphere on September 23. Is this the fault of climate change? :-)

LTC Stephen F. — Mon, 21 Sep 2015 09:01:55 -0400

I seem to remember the seasons tended to shift around the 20th or 21st of the month. I was lulled out of my thinking to learn that because the equinoxes and solstices are based on solar/lunar cycles they can shift.
Since the seasons are reversed between Northern and Southern hemispheres, I have long been curious about what happens at the equator - granted it tends to be very warm all year long at many places on the equator so it probably makes no difference to those living there. :-)
[Update] I originally posted this in humor; but, since all of the responses so far have been serious I added astronomy.
http://www.timeanddate.com/calendar/aboutseasons.html

Defining seasons

When does spring, summer, fall and winter begin?

Response by PO3 Steven Sherrill made Sep 21 at 2015 9:31 AM

PO3 Steven Sherrill — Mon, 21 Sep 2015 09:31:07 -0400

While it is true that nature runs on its own time schedule, and that can change from year to year, I do think that we as humans have screwed up this planet to a point where some of the natural phases of change are out of their natural alignment.

As for the equator, where I grew up was just north of the equator. The temperature ranged between 77 and 87 degree daily throughout the year. Occasionally we would get a storm that would drop it down to the lower 70's, but nothing lower than that. Seasonal changes were only something that was marked on the calendar.

Response by LTC Stephen F. made Sep 21 at 2015 10:17 AM

LTC Stephen F. — Mon, 21 Sep 2015 10:17:42 -0400

The seasons are based on the equinoxes and solstices. I was amused to learn that different areas of the world define the beginning of each season differently.
"People in Australia and New Zealand for example, consider September 1 as the beginning of spring. The Irish on the other hand believe that spring begins on February 1, when they celebrate St Brigid's Day. Some cultures, especially those in South Asia have calendars that divide the year in six seasons, instead of the four that most of us are familiar with."
I suppose I shouldn't be surprised that different groups of people define the beginning of the seasons differently after all different groups established the time zones with exceptions and more recently daylight savings time was initiated less than a century ago as though we could actually save some daylight :-)

Defining seasons

When does spring, summer, fall and winter begin?

Response by SSgt Terry P. made Sep 21 at 2015 11:17 AM

SSgt Terry P. — Mon, 21 Sep 2015 11:17:17 -0400

The September equinox occurs the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s Equator – from north to south. This happens either on September 22, 23, or 24 every year.

Response by MSgt Private RallyPoint Member made Sep 21 at 2015 11:43 AM

MSgt Private RallyPoint Member — Mon, 21 Sep 2015 11:43:04 -0400

It's Bush's Fault

Response by SGM Mikel Dawson made Sep 21 at 2015 11:59 AM

SGM Mikel Dawson — Mon, 21 Sep 2015 11:59:33 -0400

It was Thursday, 27 Aug. I stepped out of the house that morning at 0400 and the first thing that hit me was - Summer's over, fall's here. Every year it's a different day, but the feel and smell is the same. There is always something in the air for me, and I'm usually right. Yes, there will be warm days after that "feeling", but the summer heat is gone from the sun. Maybe it comes from the years I worked in the wilderness area and became so tuned in with the weather and nature.