Why is it so easy to hit finish day? Just screwed over 30 minutes away because I forgot to save. Why is there not an auto save just before saving the game and not after? Why is there not a "are you sure" prompt? Why doesn't my dick work? etc. etc.
Auto-save is generally a rather insignificant and underdeveloped feature that rarely gets used. More often than not people complain that it exists, because those saves appear at the top of the list rather than the most recent save. People who care a lot about perfection tend to make their own saves rather than use auto-save.
It's fairly easy to change the timing of auto-save to just before the end of day. The code is found in Mansion.gd; simply move the line
autosave()
from the beginning of function startnewday to the beginning of function _on_end_pressed.
A verification prompt could be added, though it seems kinda tedious.
That all said, I have no idea what went wrong for you. If the game crashed, then that is likely a mod's fault. There aren't many things in the game where a single day makes a huge difference, unless you waited until the last day for a slave request.
As for your dick not working, I assume it's a joke as there are no further details and this post was not made in the bug category.