"I couldn't come" - It is used in a past context or future context?

Tapas MandalIt's a bit confusing.

Maybe it's confusing because 'can' is used for both present and future.

I can't come tomorrow.
I can't come today.
I couldn't come yesterday.

CJ

CalifJimbecause 'can' is used for both present and future.I can't come tomorrow.

Is 'could' also used for past as well as future events?
Can I say "I couldn't come tomorrow" like "I couldn't come yesterday" ?

Tapas MandalCan I say "I couldn't come tomorrow"

Not just like that, no. It would have to be within a conditional structure that envisions a future situation that is imagined rather than real.

I couldn't come tomorrow even if you asked me on bended knee.
=
I would not be able to come tomorrow even if ...

Compare:

CalifJim It would have to be within a conditional structure that envisions a future situation that is imagined rather than real.

Ok Jim, then, that means if I want to use 'could' to express a future situation then I have to use some extra phrases to explicitly refer that it's a future situation unlike past situations?

Tapas Mandalthat means if I want to use 'could' to express a future situation then I have to use some extra phrases

Yes. In the general case you have to make it hypothetical, i.e., imagined.

CJ

Thank you CalifJim for these clarifications.

Tapas Mandal"I couldn't come due to some personal reasons." My question is that if someone wants to use it for past/future events then how he/she should express it? It's a bit confusing.