1. MODALS OF THE PAST

2. MODALS We use the modals to change the mode or meaning of a verb.
A tense is usually connected to time, while a modal is more connected to meaning.
I can swim. (Am I swimming now? We don’t know.)
I might leave. (Am I leaving now? In the future? We don’t know. )
I shouldn’t skip my class. (Do we know when? NO.)

3. MODALS AND TIME
Sometimes, modals can be connected to time, but the focus is on the meaning.
can/will = present/future
could/would = past

4. MODALS Modals usually have the form: S + modal + base form
They don’t change for any subject! They are super easy!
She can leave.
Can she leave?
NOT Can she leaves?

5. MODALS OF THE PAST
However, sometimes you want to use the other modals to change verbs in the past (should, could, may, etc.)
You have to use them differently in the past.
I should eat later. (RIGHT!)
Yesterday, I should eat. (WRONG!)
I must leave now. (RIGHT!)
I must leave yesterday. (WRONG!)

6. MODALS OF THE PAST
BE CAREFUL: Some modals change meaning when we use them in the past!
Students must be on time. = It is very important to be on time.
Students must have been on time. = They were probably on time. (DIFFERENT MEANING!)

7. FORM Modal + have + past participle I could go tomorrow.
I could have gone yesterday.
He should leave now.
He should have left yesterday.
He might be angry.
He might have gotten angry.

8. USE We use the modals To discuss possibility.
May
Could
Might
To discuss possibility.
If I had known about the test, I might have studied.
(It’s possible you would have)
He may not have said anything because he was worried.

9. USE We also use couldn’t have to show surprise about something!
A: The president stole a car!
B: What? He couldn’t have!!!!
(They’re not saying it’s impossible; they’re saying it’s surprising/ hard to believe!)

10. USE If I had known about the test, I might have studied.
(It’s possible you would have)
He may not have said anything because he was worried.
You can discuss past possibility using past modals.
You are not sure, so you are guessing.

11. USE
You can discuss past probability (you are 60%-100% sure) using must.
A: Why didn’t Matthew say anything to you?
B: He must not have heard me.
When you failed your first test, you must have been very worried!

12. USE Be careful – must does not mean necessity!
If we are talking about something you needed to do, use “had to”
When I got to school, I must have gone to class at 9:00.
When I got to school, I had to go to class at 9:00.

13. USE
To talk about something that could have happened (but didn’t!), use could have/ couldn’t have:
Why did you scare that bear? It could have killed you!!!
I could have applied to UBC, but I wasn’t interested.

14. USE
If it is bad that someone did or didn’t do something, use should have/ shouldn’t have or ought to have.
I failed my test! I should have studied more.
He ought to have apologized. He is very rude.
She shouldn’t have hit him.

15. USE Do not use supposed to with have!
He was supposed to have talked to you!
He was supposed to talk to you!