is x are

[beachboy]

- I needed two weeks. And now the two weeks are gone
- Two weeks is all that is needed to finish the work
- Two weeks are needed to finish the work
Which sentences are right?

[5jj]

- Two weeks is all that is needed to finish the work.
- Two weeks are needed to finish the work
Which sentences are right?

Both, though the first is more natural.

We can see 'two weeks' as a (singular) time-period, or we can see it as two (plural) units of time.