And to add to what Geoff pointed out, it might be noted that that page only lists the "debut" of particular programs, but the PBS National feed usually has many subsequent showings on ensuing nights. Depending on your station, you may or may not have access to those showings.
If you're only receiving the National feed to begin with (and not using a local station at all) as I believe the original poster might be doing, unfortunately I know of no place to get the listings for what they show on a daily/nightly basis on the National feed when it comes to rebroadcasts.
DP1 is right. It is frustrating trying to figure out what and when national PBS shows will be shown by your local affiliate (in my case, KCET in L.A.) Although KCET posts a "digital" schedule giving the dates and times of widescreen digital and HDTV programming, it is not always accurate. So I found out last night when, referring to their schedule, I tuned to KCET-DT at 9 PM to watch the 2-part series on big ships, only to discover they were re-broadcasting a Nature episode on wild horses I had already seen.
Same thing happend to me with regard to the second showing of the Warships program. I had set my HiPix to record the 2 Evolution shows and the first showing of Warship but didn't notice the latter was 2 hrs so I tried to catch it again later and failed.
In general I have found that the first showings as indicated on Seattle's pbs station:
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