Difference between last year and in the last year, and the meaning of this week in present prefect

Question

Q1: I learnt "last year" and "in the last year" are very different in meaning. In my understanding, "last year" seems to be a indivisible time frame when it is used in past simple. For example, today is 2017-03-03 and if I say:

I went to Mexico last year.

Does that mean "I went to Mexico at 2016-03-03"?

In contrast, "in the last year" seems to be used in present perfect only. And if I say:

I have been to Mexico in the last year.

Does that mean "I have been to Mexico at least once in last 365 days"?

Please correct me, it would be better if you can tell more about how to understand the direct and indirect meaning of these two phases because they are same if literally translated to my mother language.

Q2: I also heard "this week" can be used in present perfect. Is that correct? The present perfect seems to describe an action happened at an unspecified time before now. How to understand the meaning of "this week" if it could be used in present perfect?

Thanks for the help!

Answer 1

in the last year means "in the last twelve months (or so) including today".

Have you been outside the country in the last year?

If you were outside the country as recently as this morning, the questioner would expect you to answer "yes", even if your trip this morning was the only time you had been outside the country.

Since in the last year impinges on the present, the present perfect is fully grammatical.

It is equivalent to "Counting backwards from today..."

last year = during the previous calendar year (e.g. 2017 -> 2016).

Answer 2

If it's 2017 and you went to Mexico last year, then you went to Mexico some time in 2016. If you say instead,

I went to Mexico at least once in the last year

Then you went to Mexico one or more times in the past 365 days, more or less. It might have been 400 days ago. In English, many of these relative time periods are not meant to be precise. If you want to be precise, you can use exact dates:

I was in Mexico on August 1st of last year.

I was in Mexico over the (Christmas) holidays.

The present perfect describes an ongoing condition. "This week" includes the present moment, and indicates the action has been going on all this week, up to today.

He has played basketball every day this week.

The students have been studying for final exams this week.

There is more subtlety to this structure, but you'll have to let me know more detail about why you find it difficult or confusing so I can answer specific questions.

Answer 3

I disagree with the notion that "in the last year" refers to the last 12 months. Both your examples could refer to either a calendar year or the most recent 12-month period. In fact, there are many other definitions of "year", not only in English - the financial year, for example, is a fixed 12-month period that does not correspond to the calendar year. Context would have the greatest bearing on what a person meant by either "last year" or "in the last year".

"Last year" tends to refer to 12 months prior to the date in question. For example:

-"I got a bike for my birthday"
-"What did you get last year?"

One would get from this question that the person is asking about the same event under discussion (the birthday) 12 months ago. Of course, a birthday is a fixed date, but the same would be true of an event that was not fixed, for example:

-"This year I went to France for my vacation"
-"Where did you go on vacation last year?"

Although there is no fixed date for a vacation, this assumes that the person vacations every year and perhaps at approximately the same time of year. Without any further context, I think one would be reasonable in this assumption.

"In the last year" could mean "during the last 12 months" but it could equally mean "during the last calendar year". Context should determine what the benchmark is. For example, if someone were referring to data from a survey or census that was carried out annually it would be reasonable to assume that "last year" referred to the most recent complete period of that study. That could be a calendar year.

If somebody referred to something they did "last year" and they said this to you on January 1st you would assume that they were speaking about an event some 12 months ago, or at least some time ago within the last 12 months - it is unlikely you would think they were talking about something they did yesterday, even though that was technically "last year".

The only firm distinction between the two statements you quote is that saying "in the last year" specifically suggests that something happened either at any point during that period or throughout that period, rather than point to a specific time, for example:

Apple sold 216 million iPhones in the last year.

This makes it clear that 216 million iPhones were sold throughout the year. However:

Last year Apple sold 216 million iPhones.

This could mean that they sold that many all on the same day, although it is highly unlikely anyone would assume that was what it meant.

To be clear: I am not advocating that we all assume what a person means - if you don't understand the context, ask them!

Answer 4

Q1

I went to Mexico last year

If you said this in 2017, it would mean that, at some point during 2016, you went to Mexico.

I have been to Mexico in the last year

You would probably not use present perfect to make a simple statement like this, though you might use it in response to a question, as in these two examples:

Q: Have you been abroad recently?
A: Yes, I have been to Mexico in the last year

Q: Have you ever been to Mexico?
A: Yes, I have been to Mexico

In this case, the have serves to emphasise the answer to the question. Here is an example that would work as a simple statement:

I have been to Mexico several times in the past year

This is a repeated action that took place at unspecified times over a specified period (within approximately the past 365 days).

Note that in the last year is much more likely to be used about the final year of something, for example in the last year of his life or in the last year of world war II.

in the past year is only used when talking about the year to date.

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Q2

You can use present perfect when you want to talk about something that happened many times over a period.

I have interviewed a lot of people this week.

YOu could also use present perfect continuous in the same way:

I have been thinking about him a lot this week.