The English language uses past tenses in 3 different cases.
To express:
- PAST (shocking!)
- POLITENESS
- HYPOTHETICAL SITUATIONS
Past
Probably the most obvious reason for using past tenses is to talk about past times, such as
yesterday, last year, last month, a thousand years ago, when I was in Madrid, etc.
We had to make a couple of store runs.
The kids heard a screechy sound and went all silent.
While she was watching the news, her car’s alarm went off.
Politeness
Maybe even without realizing it, we do pretty much the same in Czech. We say ‚mohla‘ or ‚mohl‘ to politely ask for assistance. We can amplify this back-shift by using the progressive aspect.
Thomas, could you give me a hand, please?
Would you mind sharing this with your friends, please?
I was wondering if I could borrow your car?
Hypothetical situations
This actually works again similarly as we know it in Czech. ‚Kdybych měla..‘ or ‚Když by bylo…‘.
When talking about something hypothetical English uses back-shift.
When it’s about a hypothetical present/future situation, we use the simple past.
When talking about a past hypothetical event, we use the past perfect tense.
If I were you, I’d buy it! (present/future)
If I had known that before, I wouldn’t have gone there! (past)
If we had a skilled drummer we could start a band. (present/future)