[Grammar] This has been a tense two weeks

[kadioguy]

In Longman Active Study English Dictionary 5th EDITION:

tense adj.

example sentence:
This has been a tense two weeks.
------
Why does two weeks use a as indefinite article?

Thanks!

 

[emsr2d2]

Because here, "two weeks" is taken to mean "a period of two weeks".

This/it has been a tense two weeks.
Note the difference between that and the more standard:
The last two weeks have been tense.

It can be used for various periods of time:

That was a long three hours.
It has been a stressful six months.
I've never had a worse seven minutes.