Modals in the present and past
Generally speaking modals in the past have the following form:
- modal + have + past participle
Example:
- Present:
You should see a doctor. - Past:
You should have seen a doctor
Except for modals that express obligation,ability and lack of necessity:
- Obligation:
Present = I must / have to work hard. -- Past = I had to work hard. - Ability:
Present = I can run fast. -- Past = I could run fast when I was young. - Lack of necessity:
Present = You don't have to / needn't take your umbrella. -- Past = You didn't have to / didn't need to take your umbrella.
