When was it that the lights failed to go on one Saturday night at Gatsbys house?

The lights failed to go on one Saturday night at Gatsby's house during a significant party in F. Scott Fitzgerald's "The Great Gatsby." This moment symbolizes the decline of Gatsby's extravagant lifestyle and the disconnection between him and the guests he hoped to impress. It highlights the emptiness of the lavish gatherings and foreshadows the unraveling of Gatsby's dreams.