1) It is a long time since we last met.

=>We haven't met each other for a long time

2) When did you have it?

=>How long have you had it?

3) This is the first time I had such a delicious meal.

=> I haven't eaten such a delicious meal before

4) I haven't seen him for 8 days.

=> The last time I saw him was 8 days ago

5) I haven't taken a bath since Monday.

=> It is the first time I have ever taken a bath since Monday

*Tất cả đều dùng thì hiện tại hoàn thành

=> Cấu trúc: S + have/ has + PII.