In 1580 Gregory XIII appointed Danti as Papal Cosmographer and Mathematician and so he went to Rome where he also served on the commission to reform the calendar.
Sa 1580 Gregory XIII hihirangin Danti bilang "Papal Cosmographer at Mesopotamya at kaya siya nagpunta sa Roma kung saan siya rin nakapalabas ang komisyon upang mapabuti ang kalendaryo.