Learn Dutch: Het is nu één uur. - It is now one o'clock.

The accent marks show that it means the number "one" rather than the word for "a" or "an" (een without accents). Because you are talking about exactly one o'clock, you need the accents to specify the number.

Does uur literally mean "o'clock"?

The word uur literally translates to "hour". However, for telling time on the whole hour, Dutch uses it exactly where English uses "o'clock".

Can I put nu at the beginning and say "Nu het is één uur"?

No, because of the strict "verb second" rule in Dutch. The main verb (is) must be the second piece of information in the sentence. If you start with Nu, the verb has to come immediately after it, so it becomes: Nu is het één uur. In our example sentence, Het takes the first spot, so the verb is second and nu naturally follows it.

Do we always use het when talking about the time?

Yes! Just like in English where you say "It is one o'clock" (even though "it" doesn't refer to a specific object), in Dutch you use the pronoun het (it) as the subject when stating the time.