First network rerun date for "The Debutante Ball"?

[CKlemow]

Hey there - I recently found a cassette tape of my sister and I babbling into a cassette recorder as children and am trying to date it. At one point, you can hear some "Laverne & Shirley" dialogue in the background, which I've discovered is from "The Debutante Ball." That episode premiered on May 9, 1978... but later on the tape, I tell my grandfather than camp is over for the summer and school will start in September. I don't suppose anybody here knows what date in the summer of '78 that episode first re-ran on ABC, or how to find out... ? Thanks!