Other "This Day in Music History" sites I have noticed show release dates of singles that are incorrect. They mistakenly show them as being on the day that a singles chart came out (Saturday). No one releases songs on weekends. Anyone in the music business knows that songs are released on Monday's so that radio stations can add them to their playlists. The trade magazines (R&R, Billboard & Gavin Report) took reports on Tuesday and then reported them the following week. Any single that was released later than that would not make the trade papers until another week.
Bottom line: If you see a single that was reported to be released on the day the chart came out is probably incorrect.