Quick Tip: Using FOR/SINCE in the Present Perfect

Yet another common challenge for English learners is how to correctly use for and since in the present perfect.  Take a look at these common mistakes for beginning students:

       We have been traveling around the United States since one month.
       We have been traveling around the United States for one month.

        She hasn't taken a vacation since a long time.
        She hasn't taken a vacation for a long time.

SINCE when?  FOR how long?

If you don't know whether to use for or since, ask yourself...

for HOW LONG?
...two days
...five minutes
...a thousand years
...a long time
...a second
...the rest of my life
...a couple weeks

For is used to express the duration of time. 

since WHEN?
...last Tuesday/month/year/weekend
...November 25
...1980
...3:00 pm

We can also use a dependent clause (subject+verb) after since:
...we got married
...I moved to New York
...he quit his job

or a gerund
...graduating highschool
...buying our new house
...writing my first book

Since is used to express a specific point in time. 

Using the Past Tense with Since

Note that when using since, we sometimes use a combination of the present perfect in the independent (or main) clause and the past in the dependent clause.  Take a look at these examples:

        They haven't seen their grandmother since the family went on vacation last year. 
                 present perfect                                                      past

        Since I moved to Lisbon, I haven't eaten pancakes.
                    past                         present perfect

We can also use the gerund in the dependent clause, which gives the sentence a more general time frame and doesn't overtly identify the subject:

        Since having a baby, she has lost weight quickly.
                  gerund                   present perfect

        We haven't seen them since visiting last Christmas.
               present perfect               gerund

If you have any questions, just post below...I hope these tips help you!