Understanding the sequence of tenses will help you do many things:
It helps you explain what someone else said (indirect quotations)
It helps you with conditional sentences (using the word "if")
It helps you make sentences using the word "wish"
Here are some examples:
Someone says, "I need to go to the store."
She said that she needed to go to the store.
You change "need" to "needed" but the situation is still in the present. This is a strange thing about English, but many Americans do this properly without thinking about it.
Here’s another example:
If you could meet me at the airport, I would be grateful.
In this situation, "can" changes to "could." Why? Because "if" is present and the sentence is conditional. We will practice conditional sentences in Lessons 11, 12, and 13.
Here’s an example using "wish":
I wish I had been at the party last night.
This sentence indicates that something did not happen in the past, but it uses the past perfect to express it. Confused? Take a look at the chart below and then go on to the next three lessons.
The chart above is is also found in the Yellow Level, Lesson 16.