Present perfect VS Past perfect

Both present perfect and past perfect talk about something that happened before a point in time (reference point).In the present perfect, our reference point is the present.In the past perfect, our reference point is in the past.

Present perfect An action that started in the past and continues to the present.I have lived in this city for six months.

An action that happened before now (unspecified time)I have been to Japan twice.

How to form the present perfect:HAVE / HAS + past participle

Examples of the present perfect:1) My mother has just gone to the store.2) Janet has lived abroad for five years.3) I havent seen the new movie yet.4) Have you finished your homework?

Its very common to use the contractions ve and s in the present perfect:1) Ive been to Japan three times.2) My mothers just gone to the store.3) Janets lived abroad for five years.

Past perfect An action that happened before a time in the pastWhen I arrived at the office thismorning, I discovered that I had left my computer on the night before.

How to form the past perfect:HAD + past participle

Examples of the past perfect:1) I went to Japan in 1988 and 1991.2) I turned 10 years old in 1994.I had been to Japan twice by the time I was 10 years old.

1) My husband ate breakfast at 6:00 AM2) I woke up at 7:00 AMWhen I woke up this morning, my husband had already eaten breakfast.

Its common to use the contraction d in the past perfect: Id traveled to five different countries by the time I was 20 years old.