The tenses are divided into 12 main categories depending on their time frame i.e. Present, Past and Future.
I want to know then under which time frame these sentences can be categorised.
It could not have snowed on 25th of September.
It would have been a disaster without your help.
It should have outperformed the other tests.
Under which type we can keep these sentences? There can be many other variations but basically I want to know how we can know their time frame?