Each world has its own “time setting”, as the one in the settings menu only applies to new world generation. That means if you set one character to spawn at Winter, all of them will; one won’t be able to spawn earlier in the year unless the setting is changed before a new world is generated. With that in mind, that’s still a very valid point; if a character dies at day 3 of Winter and a new one spawns at day 1, how is the second character able to find a corpse and items that should not technically exist yet?
I’m partial to your confusion. I never thought about it this way. Maybe you are spawning next year, but because “years” are not part of the engine’s logic or something they don’t advance the days properly. Perhaps this is done so that item durability/freshness doesn’t degrade way more than it should, giving characters who spawn in later years a bigger disadvantage than of those who came before them. But I digress, dying and spawning with a new character should have some consequences. This might have been an oversight.
Maybe the items/corpse can be marked on char death, hidden, then appear again right after the date of death passes so new characters can collect the loot. But then, what prevents newer characters from camping death spots until objects simply start popping into existence? Someone else might give us a proper explanation.