Have a bless day in Arabic?

To say "Have a blessed day" in Arabic, you can say "أتمنى لك يومًا مباركًا" (Atamanna laka yawman mubārakan). This phrase conveys good wishes for a day filled with blessings. You can also use "عسى يومك مبارك" (ʿAsā yawmuka mubārak) for a similar sentiment.