Two kinds of air dates are listed. For seasons one and two, the date is PTEN's preferred airdate, Wednesday of each week.
However, by the end of season two, with the emergence of the Paramount and Warner Bros. networks, the majority of stations were showing B5 on other nights; so the dates for season three and beyond are "week of" dates, the first date (a Monday) on which stations are allowed to broadcast the episode in question.
Many stations broadcast each episode twice, once during the week and again on the weekend.
Consult your local listings to find out which night B5 is on in your area. The Air Times page may prove helpful.