Check the official Japanese(!) page, [http://www.allcinema.net allcinema] or the [http://cal.syoboi.jp Japanese TV Guide] (explained [[here]]).
===First Aired/Released and Finished Airing/Release===
Those are the first and most precise air/release dates worldwide. Most of the time it's Japanese. Check the official Asian page, [http://cal.syoboi.jp Japanese TV Guide] (explained [[here]]) or other pages [[Where to find release-dates for Anime|listed here]].
Indefinite dates, with day or month given as ??, are accepted when there is no other accurate release date available worldwide.