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:
1. If + Present Simple, Future Simple ( will + V1)
If Kate works hard, she will get a high salary.
2. If + Present Simple, Present Simple
Water turns into ice, when the temperature falls below 0.
3. If + Present Simple, Imperative
If you don’t understand, read again the material.
4. If + Present Simple, can/must/may + bare infinitive
If you go to London, you can see famous statues.