Complex sentence: The evening meal is scheduled for a specific time and all potlatch attendees are expected to attend; it is the most significant spiritual and social event of the potlatch and is treated as such by the attendees.
Split into simpler sentences: The evening meal is scheduled for a specific time and all potlatch attendees are expected to attend. It is the most significant spiritual and social event of the potlatch and is treated as such by the attendees.