Feriae - Roman Holiday - Dies Ferialis

Definition: Feriae were Roman holidays, generally of one day's duration despite the plural form. On the feriae lawsuits and other business were suspended. There were private feriae and public ones. Of the public feriae there were three types. The feriae stativae were annual holidays with a fixed date on the calendar. The feriae onceptivae were annual holidays, but their date changed depending on what priests or magistrates decided. The last type was the feriae imperativae, which were irregular, and proclaimed by dictators and consuls. The feriae imperativae tended to be more somber.

Source: Festivals and Cereminies of the Roman Republic, by H.H. Scullard.