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.
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. so B is wrong in grammar.
Of course 'could' is the past form of 'can' but also 'could' includes 'possibility' so I think B is possible.
I wonder B is wrong and absurd? (especially in grammar)
Best Answer
The second case is good English in a subjunctive mood. Consider this exchange:
This is indicative mood: it expresses an expected future, not merely a possible one.
The positive subjunctive is a little more common. I think negative subjunctive is most likely a response or amendment to a previously expressed or thought positive subjunctive.
By the way, this negative subjunctive future was recently used in the TV show The Last Man on Earth when the title character said,
It's particularly funny because in the story the characters believe they actually are the last people on earth, so the indicative mood would have been appropriate if it hadn't been a quote.