I've done some newspaper research, and the first five episodes originally aired as a mini-series during the week of March 9th, 1987. Many stations that picked up the full series re-ran the mini-series shortly before the actual debut of the series on September 21st - some the week before, some earlier. The 10th episode did air on September 21st, officially starting the regular series. All mentions of the start of the series in the newspapers say it debuted on that date.
If you notice on the DVD releases, during the closing credits. there is a voiceover of Teddy saying to be sure to watch the new series which starts "next year." This is why.