Okay, I just got back from my local library, and here are the dates in which no new episode aired:
November 24-25, 1983 (2)
November 22, 1984 (1)
January 21, 1985 (1)
November 28, 1985 (1)
July 4, 1986 (1)
November 27-28, 1986 (2)
Circa Summer 1987
November 26-27, 1987 (2)
November 24-25, 1988 (2)
January 2, 1989 (1)
January 20, 1989 (1)
March 6-17, 1989 (10)
Could there have been staggered weeks (weeks ending on different days, instead of Fridays) during the summer of 1987, that would explain the total daytime episode count (1,578)?