prepositionsword-choice
Which of these sentences is correct?
The importance to eat fruits and vegetables of different colors has been demonstrated at various occasions.
The importance to eat fruits and vegetables of different colors has been demonstrated on various occasions.
They are synonyms. Similar to what RegDwight pointed out, there is usually a connotation of many with "various," whereas "different" often refers to distinctions between 2 things.
The usual idiom is "on the outskirts". Don't ask why, it's an idiom.
Best Answer
The preposition that goes with "occasion" is usually "on", and never "at" (unless by "occasion" one means an event or gathering, which is not the case here), so "On various occasions" sounds more natural. Note, similarly, that we can also say:
but never:
I would also suggest "many times" or "several times" as alternatives to "on various occasions".