"At predetermined times" are words commonly used to describe things that are scheduled or planned in advance. However, there are many synonyms that can be used to express the same idea. Some of these synonyms include "on a set schedule," "as per a prearranged schedule," "according to a predetermined plan," or "at specified intervals." Other options might include "regularly scheduled," "in accordance with a preset timeline," or "according to a preplanned timetable." No matter which synonym you choose, the key emphasis is that the event or activity takes place at a specific, predetermined time, rather than on an ad-hoc or impromptu basis.