From the Big Bang to Dark Energy

The seasons are absolutely not arbitrary. They follow predictable patterns and are controlled by the position of the Earth it orbit because the axis of Earth's rotation is tilted. There is specific astronomical point that can be easily determined that mark the beginning and end of the season and that point occurs at a specific moment in time. Nothing arbitrary except the tilt of the planet. Other planets with different tilts have different seasonal cycles.

Even on Earth, the number and type of seasons is a somewhat regional phenomenon. It's true that in some region the local geography might be as important as the effect caused by the axis tilt, but generally it's the tilt.

Check out this interesting video by a Prof at University of Tokyo (video is English.) Whole thing is good, as is the course, but around 8:00 where he talks about how equatorial regions can experience two "summers" but during the time temperate regions experience fall and spring. https://www.coursera.org/learn/big-bang/lecture/g9A2t/1-1-night-and-day-and-four-seasons

From the Big Bang to Dark Energy. Free course from the University of Tokyo

Hey, I’m a fellow incoming student at the University of Arizona to study a double major in Astronomy and Physics! While I can’t answer your question, I’d love to share some resources I found really useful to explore astrophysics without any rigorous academic background. This is my favorite online course that covers essential topics in cosmology, introducing the Big Bang theory, dark energy, dark matter, antimatter, cosmic inflation, etc: https://www.coursera.org/learn/big-bang. I had so much fun learning truly mindblown theories and the professor did an amazing job explaining these concepts for the general audience.

Also, I recommend exploring this website: worldscienceu.com. World Science U is adding tons of new courses on all kinds of astrophysics (and other science) fields taught by leading scientists at an introductory level for the general audience. I took a 1-week masterclass (which they no longer offer but I believe they are transforming these into full-fledged courses) on inflationary cosmology, explained by the theory founder Alan Guth himself!

Besides, I love watching YouTube videos from Minute Physics, PBS Space Time and FermiLab. You have probably heard about these channels before. They did a spectacular job in making challenging topics simple enough to follow. I’m sorry that these are not related to what you asked but I hope you might found these helpful. Also, I’d love to get to know you more and make friend with you on Reddit. It’s nice to have friends who have similar aspiration!