To speak about possible situations in different periods you should use Conditionals.
There are three types of Conditionals.
In each sentence there are 2 parts: the if-clause and the main-clause.
Type 1 Conditionals.
This type describes a real or very probable situation in the present or future.
Use these structures:
- If + Present Simple, Future Simple ( will + V1)
If Kate works hard, she will get a high salary.
- If + Present Simple, Present Simple
Water turns into ice, when the temperature falls below 0.
- If + Present Simple, Imperative
If you don’t understand, read again the material.
- If + Present Simple, can/must/may + bare infinitive
If you go to London, you can see famous statues.
Study the information about the 2nd Conditional.
Type 2 Conditionals.
This type of conditionals expresses an improbable and imaginary situation
which is unlikely to happen in the present or future.
Use this structure:
If + Past Simple, would / come/ might + bare infinitive
If I had a lot of money, I would buy a new car.
You can use were instead of was after if.
If I were you, I would talk to him.
If Sam was/ were here, he would tell us how to react in this situation.
Study the information about the 3rd Conditional.
Type 3 Conditionals.
This type expresses imaginary situations in the past. They refer to past situations that did not happen.
If + Past Perfect, would/could/ might + have+ past participle
Kate missed the plane yesterday. If she hadn’t missed the plane, she wouldn’t have been late for meeting yesterday.
If Mike had called earlier, I would have told him about the party.