What is considered a "New Fruit" for Bracha Shechiyanu

If fruits and vegetables are available a whole year round( imported from all over the world) and grown domestically, what constitutes a “New Fruit” come Rosh Hashanah; that I can make a Shechiyanu on it?

And if it is based on whether I have had this fruit recently, how much time has to pass before i can make the bracha Shechiyanu?