The Proto-Indo-European word *h₁en-
Word *h₁en-
Meaning year
Synonyms *wet-, *(h₁)yēro/ehₐ, *hₐetnos

Comments
Mallory J.P. and Adams D. (2006)

Other words that might be of interest
*kēs(k̂)ehₐ ‘time’, *kʷóm ‘when’, *kʷodéhₐ ‘when’, *sem- ‘at one time, once’, *posti ‘after’, *wételos ‘yearling’