MB darling, didn't the *first* episode of DS debut at 3:30 p.m.? sorry to be persnickety...
According to the DS Almanac, DS debuted at 4:00pm, then it moved to 3:30 on April 2, 1967, and then back to 4:00 on July 15, 1968.
(Though, of course, many stations aired it at various other times. For instance, for a time it was shown at 2:30pm in Boston, MA and at 8:30am(
) in Providence, RI.)