Generally, the Japanese/Chinese/Korean/Asian air date is the first airing of an episode. Check the official Japanese/Chinese/Korean page, [http://www.allcinema.net allcinema] or the [http://cal.syoboi.jp Japanese TV Guide] (explained [[TV schedule|here]]).
The Western air date should only be used if the Western airing is '''materially earlier''' than the Asian one. Otherwise, use the air date in the home market. For example: