What are 20 years called?

What are 20 years called? Word Origin for vicennial C18: from Late Latin vīcennium period of twenty years, from Latin vīciēs twenty times + -ennium, from annus year.

Word Origin for vicennial

C18: from Late Latin vīcennium period of twenty years, from Latin vīciēs twenty times + -ennium, from annus year.