Today is the weekend. Weekend has been attempted here already. “Holiday” or “holidays” is also easy enough (dies feriae). But what if I want to say “today is a day off work” or a “a day without work”?
You could say:
That is, a day of leisure or free from business.
This word otium was used in Cicero's defense of Gnaeus Plancius, in which he quoted Cato as saying:
clarorum virorum atque magnorum non minus otii quam negotii rationem exstare oportere. (Pro Plancio)
That eminent and great men ought to lay down a regular plan for their leisure as well as for their business.
“Otium” is certainly possible, but it often has a slightly negative implication (idleness, laziness). A more neutral term might be “requies”, which is used also in Christian writings in connection with the Sabbath, e.g. in the Vulgate version of Ex. 31,15 where the Sabbath is called "requies sancta Domino". The day of rest could thus be "dies requietis", or simply "requies".