We can make unreal conditionals in the past tense as well as the present and future tense. These past tense conditionals are used to talk about alternative outcomes to past events and situations. In other words, they tell about how things could have been different.
Unlike present and future unreal conditionals, past unreal conditionals cannot ever really happen because they are already in the past.
These sentences are formed using: If + past perfect, (then) + would + have + past participle
Although we usually use the past perfect, we can also use the past perfect continuous when it is appropriate.
Here are some examples of past unreal conditional sentences.
If I had learned about computers earlier, I would have been a better programmer.
If I had hung my keys up, I wouldn't have lost them.
If I had been running outside, I would have gotten wet.
Occasionally, we mix past and present times in unreal conditionals.
Sometimes, the present could have affected the past.
If I could sing, I would have gone to karaoke with you.
In this example, I cannot sing in the present or in general, so I did not go to karaoke in the past. The unreal conditional about being able to sing is still applicable for the present, so we do not say 'If I could have sung.'
Sometimes, the past could have affected the present.
If you hadn't stayed up so late, you wouldn't be so tired today.
In this case, the unreal conditional, staying up late, happened in the past, but it affects the way you feel today. That is why we don't use the past tense in the main clause.
Exercise
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