Example: Drum Corps International
By DCI guidelines, if your 22nd birthday is after June 1st, but before DCI Finals, you are able to march that summer. If your 22nd birthday is before June 1st, you can no longer march. In both of these cases you are considered "aged out".
In the past in North American circuits, members were eligible for competitive junior corps if their 22nd birthday was after the date of the circuit's championship.