1) This is not the first time that the residents of the capital have had to suffer such inconveniences. (This is collected from a daily newspaper)
2) "This is not the first time that the residents of the capital have to suffer such inconveniences.
I know the rules of "have to/has to, had to ". But I haven't found anything on "have/has had to ".
Would somebody tell me the difference between those sentences?
"have had to" and "had had to" are the perfect forms of "have to"/"has to"/"had to", so it operates very similarly to the difference between the simple and perfect in other cases:
I have to eat before noon
compared to
I have had to eat before noon every day this week
The first is an obligation one time; the second specifies a recurring obligation started in the past but with current relevance.
The difference between "had to" and "had had to" is similar but in the past instead of the present; the past perfect "had had to" would express a past obligation starting before another past event with continued relevance to the second past event.
I had to eat before noon last Friday to be able to catch my bus
compared to:
I had had to eat before noon every Friday last year to be able to catch my bus
Phrases starting with the first time are "shifted back" into the past. So if it's something you are doing now, you use present perfect:
This is the first time I've eaten octopus.
If it's something that will (or might) happen in the future, use the present:
The first time you travel abroad, you will need to get a passport.
If it happened in the past, you can use past perfect:
That was the first time I'd used a computer.
But in this case, simple past is also OK:
That was the first time I used a computer.
But beware! Phrases starting with the last time follow different rules in the present and past:
This is the last time I eat octopus.
That was the last time I used a computer. (Past perfect is not OK here.)
I am not competent to explain these rules. But if you break them, you will sound foreign.
