The Proto-Indo-European word *kʷóm
Word *kʷóm
Meaning when
Synonyms *kʷodéhₐ

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

Other words that might be of interest
*wet- ‘year’, *h₁en- ‘year’, *kēs(k̂)ehₐ ‘time’, *sem- ‘at one time, once’, *(h₁)yēro/ehₐ ‘year, new season’, *hₐetnos ‘year’, *posti ‘after’, *wételos ‘yearling’