Two of the more confusing tenses in English are the present perfect and the past perfect. What makes them so is both describe continuous actions. To illustrate, let’s take a look at the following sentences:
1) Last night, I walked my dog.
2) I have walked Bucky every night for the last two years.
In the first sentence, I am doing the action, ‘walk’, only once. In the second sentence, I am describing something that has taken place on a number of occasions in the past and continues on till today (meaning tonight I will most likely walk Bucky).
The first tense is the simple past (if you look at my description it is very simple). The perfect tenses, on the other hand, aren’t so simple. To show you what I mean, let’s take a look at the past perfect.
1) Before I moved to California, I had walked Bucky in the mornings, not at nights.
Whenever we use the past perfect, we want to use the following tense:
Past Perfect: Had + Participle (plus another verb in the Simple Past)
Why use past perfect in this sentence? Well, if you notice, I am talking about two events that happened in the past: my walking Bucky and my moving to California.
Whenever you are dealing with two events in the past, one of which started or happened before the other, you must use the past perfect tense to describe the event that started first.
First Event: I walked Bucky in the morning = Past Perfect Construction
Second Event: I moved to California = Simple Past
Another way to think of the past perfect is with specific dates. Let’s say I moved to California in 1984. I walked Bucky every morning from 1981 to 1984. The sentence implies that once I moved to California I no longer walked Bucky in the morning. That is, an event that happened repeatedly in the past stopped when another event happened. That interrupting event uses the simple past.
Now let’s try a couple of practice questions:
1) After she graduated/had graduated from high school, Jessica decided/had decided to backpack through Europe.
2) Though he studied/had studied the entire weekend, Bobby was only able to get a B- on his Calculus mid-term.
For sentence #1, we have the first event: Jessica graduating. This event must be in the past perfect tense: had graduated. The more recent event, her deciding to backpack, is in the simple past: backpacked.
For #2, the first action is the studying, so we need had studied.
#1: Present Perfect: Has/Have + Participle = describes action/event that happened in the past and continues in the present.
#2: Past Perfect: Had + Participle = describes an action/event in the past that happened before another action in the past.
#3: Whenever we use the past perfect, we must also have another verb in the sentence that is in the simple past.