dies faustus /fösˈtəs or fowsˈtŭs/ noun

A lucky day

dies festi /fesˈtī or -tē/ or dies feriae /ferˈi-ē or -ī/ plural noun

Days of actual festival

dies infaustus /in-fösˈtəs or in-fowsˈtŭs/ noun

An unlucky day

dies irae /īrˈē or ērˈī/ noun

1. The day of wrath
2. The day of judgement (from a Latin hymn)
3. The hymn itself, used in the Mass for the dead

dies nefasti /ni-fasˈtī or ne-fäsˈtē/ plural noun

Days on which a judgement could not be pronounced and on which assemblies of the people could not be held in ancient Rome

dies non /non or nōn/ noun

A day on which judges do not sit, or one on which normal business is not transacted