past modals

today, I learned past modals.

Generally speaking modals in the past have the following form:

• modal + have + past participle

Use should have to say that a different action was recommended in the past.
ex- You should have taken the rest earlier, because it's already time you should go.


Use could have to talk about possibilities if something had been different in the past.
ex-if I had took the holiday, I could have gone to the Australia.


Use would have to imagine a result (if something had been different in the past)
ex-if I hadn't brought umbrella, I would have gotten wet in the rain.

	Modals in the Present	Modals in the Past
Obligation	You must / have to stop when the traffic lights are red.	You had to stop.
Advice	You should see a doctor.	You should have seen a doctor
Prohibition	You mustn't smoke here.	You mustn't have smoked there.
Ability	I can run fast.	I could run fast. now I am old.
Certainty	He has a Rolls Royce. He must be very rich. He can't be American. His English is terrible.	He must have been rich. He had a big house and an expensive car. He can't have written that poem. He was illiterate.
Permission	Can I go out?	She could drive her father's car when she was only 15.
Possibility	It may / can / could / might rain. It's cloudy.	I guess it may / can / could / might have been Lacy on the phone.
Lack of necessity	You don't have to / needn't buy any tomatoes. There are plenty in the fridge.	You didn't have to / didn't need to buy tomatoes.