It wasn't even always that complicated, it is easy to observe the seasons. You always know what season it is because you know what the last season was. You are going to know winter is on its way just based on however many years you have observed it. It wouldn't be like people who didn't keep track of years wouldn't know to prepare for winter. Then you have things like the zodiac, where they simply observed where the sun was in relation to the stars behind it and drew significance with what that might have meant based on the season and significant climate or weather events and so on.

Ever see something wired up with electrical wires and there is just bundles of crazy wires all jammed in together and you wonder how you would even know what each of those wires even does? A circuit board is just a way to connect all those tiny components with tiny little electrical connections. The real magic is how they create them to efficiently utilize the least amount of space. Like packing a ton of stuff in a little suitcase. Imagine you had an electronic that had dozens of little electrical components to connect together. If you start using wires it quickly becomes a mess no matter what you do. Those little circuit boards can connect all the little parts with little space, and better than that they can basically be printed out with machines and cut to shape and heated up and all the little chips just get shoved into their tiny holes and get soldered into place. You can wire tons of stuff together in a tiny space just by making it small enough and finding the most efficient way to connect them together that uses the least amount of space or fits a shape that the circuit board needs to fit into.