Today, I(non native speaker) read a question on a Q&A in my nation. The question is 'what is difference between A and B?'

A. I can't get up at 4:00 tomorrow.<br>
B. I couldn't get up at 4:00 tomorrow.

everybody(we are non native speaker) said 'could' is the past form of 'can' so you can't use "couldn't" with tomorrow. Because 'tomorrow' means future tense not past tense.

Of course 'could' is the past form of 'can' but also 'could' includes 'possibility' so I think B is possibe.

I wonder B is wrong and absurd?