Student Stumper 50: “Last” vs. “Past”

QUESTION: What’s the difference between “last” and “past”?  Can I say “the last year” and “the past year”? Do they mean the same thing?

ANSWER: We can use both of those phrases, but they don’t necessarily mean the same thing. Anytime there are similarities, we must figure out where exactly there’s overlap.

Structurally, the phrases are the same:
[definite article] + last/past + [period of time]
the last/past year
the last/past hour
the last/past 24 hours

Biber et al. list “last” as semi-determiner, which is very much like an adjective, but functions to help us with references (280). Which year, hour, etc. are we talking about? Semi-determiners also combine with regular determiners, in this case “the.”

“Past” is only listed as an adjective in the dictionary, so the overlap is going to be with these two words used before a noun. However, in terms of form, “last” can be used with a determiner or alone as a time marker:
last year
last week
last month
It’s correct to say, “Last year I went to Bermuda.”
I can’t say, “Past year I went to Bermuda.

In terms of meaning, “last year” refers to a calendar year. It’s now 2020, and in 2019 my family took a trip to Bermuda. In other words, we went to Bermuda last year.

“Last year” can be an adverbial, as seen in the previous example, or a noun phrase:
Last year was a lot of fun. (subject)
I think we can put last year down as a good one overall. (direct object)
We can’t substitute “past year” in these two examples without making other changes.

At first glance, there’s not much difference between the definitions listed first in the dictionary:
last (determiner, adjective) most recent
past (adjective) having happened, existed, or been experienced before now
The second entry seems like a wordy version of “recent,” doesn’t it?

But the second definition of “last” gives us our first difference to hone in on:
last (determiner, adjective) at the end, after everyone or everything else
Aha! That definition introduces the idea of a sequence with clear boundaries.  There’s a clear end to 2019 and a clear beginning to 2020. Last year is over. A new year has begun. “Last” can be used to refer to the final person or thing that comes after others:
the last person in line
my last day on the job
the last day of school
Note the use of prepositional phrases to specify the set of people or things. We can’t substitute “past” in these examples. It stands to reason, that “in the last year” could refer to the final year in a set of years:
I worked in Boston from 2001 to 2005. In the last year (my final year), the commute became very difficult.

Let’s return to that wordy definition of “past.” It helps us by making a connection to now, the present moment.
I’ve been working on this project for the past year.
Over the past year, we’ve made a lot of progress.
We’ve made significant gains in the past year.
Use of the present perfect clarifies the connection between the past and the present. The period in question (12 months) extends up to this point in time.

Now here’s the gray area. Let’s change those examples and use “last.” Would they be correct?
I’ve been working on this project for the last year.
Over the last year, we’ve made a lot of progress.
We’ve made significant gains in the last year.
I can’t find confirmation in my books, but my gut tells me these substitutions are acceptable and don’t necessarily change the meaning. Personally, however, I’d go with “past” if I were referring to the past 12 months (and not the last calendar year).

The overlap in meaning may increase with certain prepositions, namely in and within. If you want to refer to a number of instances within a recent period, I can see either “last” or “past” being used. For example, medical forms ask questions such as, “In the last six months, has your child had close contact with a person who tested positively to TB?” Here “in the last six months” is that same as:
within the last six months
in the past six months
within the past six months

A colleague in the UK noted that “past” works well for longer periods of time:
the past few years
the past several weeks
In contrast, “last” serves to mark the most recent period or event:
last month (the month before this one)
at our last meeting (the one that took place most recently)
I appreciate these observations.

In short, “last” and “past” have some overlap. A guideline is to use “last” for the final period of time in a set and “past” for a period of time that continues to the present.  For the sake of clarity, I’d use “last year” to refer to the calendar year before this one and “the last year” to refer to the final year in a set. I’d give preference to “the past year” for a period of 12 months that began 365 days ago and continues up to now.

Thoughts? Feel free to agree or disagree. Additional examples are welcome.

Sources:
Biber D. et al. (2007). Longman grammar of spoken and written English. Essex: Pearson Education Limited.

Bullon, Stephen. (Ed.) (2008). Longman dictionary of American English. Essex: Pearson Education Limited.

Featured photo by geralt. Retrieved from https://pixabay.com/illustrations/banner-header-question-mark-1090827/.