Much confusion is caused to English speakers by the way in which Italians express centuries from 1000 a.d. to 2000 a.d., so let’s try to clear it up:
When Italians say novecento, they do not mean the year 900 a.d., they actually mean the 1900s, or 20th century.
So the seicento is the 17th century, and so on.
The easy way to work it out is to add 11 to the number before cento:
Ottocento – 8 plus 11 = 19 – the 19th century.
But if Italians say secolo, the meaning follows the English language pattern, so the ventesimo secolo is the 20th century.
So, which century are we in? Il ventunesimo secolo.