The past tense is sometimes used in English to refer to an unreal situation. So, although the verb tense is in the past, we are actually talking about something that didn't happen. This is often the case in conditional sentences when we are talking about a hypothetical situation that might exist now or at any time. We call this use of the past tense "the unreal past".
The unreal past is used after conditional words and expressions like if, supposing, if only, what if; after the verb to wish; and after the expression I'd rather.
Conditional words and expressions
The expressions if, supposing, if only, what if can be used to introduce hypothetical situations and followed by a the simple past tense to indicate that the condition they introduce is imaginary.
- Supposing an elephant and a mouse fell in love.
- What if we painted the room yellow?
- If you went to the movies, I would babysit.
- If only I had more money, I could go to the movies too.
These expressions can also introduce hypothetical situations in the past and then they are followed by the past perfect.
- If only I hadn't kissed the frog.
- What if the elephant had stepped on my phone?
- Supposing I had given that man my money.
The verb to wish is used with the unreal past when we want to talk about situations in the present that we are not happy about but cannot change.
- I wish I had more money.
- She wishes she was beautiful.
- We wish we could come to your party.
When we want to talk about situations in the past that we are not happy about or actions that we regret, we use the verb to wish followed by the past perfect.
- I wish I hadn't said that.
- He wishes he hadn't bought the car.
- I wish I had taken that job in New York.
When we want to talk about situations we are not happy about and where we want someone else to change them, we use to wish followed by would + infinitive.
- I wish he would stop smoking.
- I wish you would go away.
- I wish you wouldn't squeeze the toothpaste from the middle!
Preferences using "I'd rather" and "It's time"
I'd rather and it's time are also followed by the unreal past. The verb is in the past tense, but the situation is in the present. When we want to talk about a course of action we would prefer someone else to take, we use I'd rather + past tense.
- I'd rather you went.
- He'd rather you called the police.
- I'd rather you didn't hunt elephants.
The stress can be important in these sentences, to show what our preference is.
- I'd rather you went. (instead of me)
- I'd rather you went. (instead of staying)
- He'd rather you called the police. (instead of me)
- He'd rather you called the police. (instead of the firemen)
Similarly, when we want to say that now is a suitable moment to do something, either for ourselves or for someone else, we use it's time + past tense.
- It's time you paid that bill.
- It's time I went home.
- Don't you think it's time you had a haircut?