i made a typo in my description thats why they're only 90 days lol i meant to fix that
another thing that could be cool is if moving east and west could affect the sun/moon position in the sky like it does in real life. also, trees, except spruce, could have their leaves all die during late fall and winter.
if the x or z axis could be the equator, that could also affect day lengths and leaf/grass colors during the different seasons.
world generation could be changed too; biomes like cold taiga, snow plains, ice spikes, cold mega taiga etc. could generate far north and south, say 75000+ blocks from the equator and get more extreme and have longer, even 24 hour days or nights dependihg on season the further in you go (i know the whole map is 30 million blocks or something in all directions, but explorers won't wanna travel that far)
biomes like taiga and mega taiga could spawn after that closer to the equator but still far
biomes that are any forest or plains, swampland, would go next
and at the equator and nearby would be jungles, deserts, mesas, etc.
biomes like extreme hills, oceans, rivers, etc would be spread throughout the world, as they can be found in places that are warm or cold.
pretty much i just want a mod that makes the minecraft world like the actual earth lol