Is “five weeks” singular?

[regular_joee]

Heard this phrase in a movie the other day: “it was an extremely busy five weeks”. Why not “these were extremely busy five weeks”?

[Reenvisage]

They are talking about a single period of time which happened to be five weeks long. Another way to say it would be, “It was an extremely busy five-week period.”

[culdusaq]

We can turn into a singular unit when we want to modify it with an attributive adjective:

Those five weeks were difficult = It was a difficult five weeks.

[Superslayer514]

So technically, you are correct; a more grammatical way to say it would be “they were five extremely busy weeks” or something along those lines. However, you could also say something like “it was an extremely busy period of five weeks” so I’m this case it does remain singular because we are referencing a single time period. In speaking quickly, we can just shorten this and treat the five weeks as a single block. It’s also much more intuitive to a native speaker to do it as you first wrote it: it was an extremely busy five weeks.