The rules used when determining whether or not items may be deleted are:

• Past: Anything (playlist, video, graphic, event) that lies completely in the past cannot be deleted. 
• Present (on air): Playlists and graphics that are currently on air may be deleted, but only after a warning. Videos that are on air cannot be deleted but skipped by clicking the "Play Next"  button.
• Future: Anything (playlist, video, graphic, event) that lies in the future may be deleted without warning.