Complex sentence: Raceway Park also traditionally stages an extensive program on the Saturday night of Memorial Day weekend (late May), the night before the Indianapolis 500 event at IMS, serving as something of an unofficial preliminary event to the far more famous one.
Split into simpler sentences: Raceway Park also traditionally stages an extensive program on the Saturday night of Memorial Day weekend (late May) called the Night before the 500. The event is held the night before the Indianapolis 500 event at IMS, serving as something of an unofficial preliminary event to the far more famous one.