Eat mainly plants
Agreed? So why isn't it smpler?
If you go to a farmers' market you will find plant foods which are in season that have been grown locally or reasonably locally. If you have a garden and grow vegetables you will have plants for consumption to hand and what grows in a given season is what you eat.
Now remove those two options. You don't have a vegetable garden or it produces only some of your needs, so you go to the supermarket or greengrocer to buy food for the balance. In those shops you'll be faced with an array of fruits and vegetables in season and out of season and, except for occasionally, there won't be huge variations in price or in appearance of fresh produce. And isn't this dilemma the one faced by most people?
What do you do?
If you are really trying to eat seasonally you'll wander around trying to recall what's in season when, fruit is somewhat easier but what about vegetables?
In simpler former times newspapers used to publish lists of foods in season making it easier for the shopper to locate the best tasting bargains for the week. Now the competing supermarket giants compete to get you in the door to buy boxes and cheap (?) petrol, reccipe books tell you to eat in season as if a divine inspiration should descend and those of us who live in temperate or tropical climates aren't a whole lot wiser.
I'm curious: how do you decide what is seasonal when you go into a shop ...