The show(s) are monitored (seasons and episodes). On the left of the calendar it shows yesterdays show(s) 31st. Which do not appear in the Calendar on Sunday (Yesterday).
The air date on The TVDB is correct.
I saw this but i am not sure if this ever got implemented/changed.
The only thing that comes to mind is the items aren’t showing up due to something with the dates, but we’ll need to get the result of the API call to verify.
In order to get the result of the call in Chrome open up the Chrome dev tools (F12), go to the networking tab, open up the calendar page and find the call to api/calendar that looks like this: api/calendar?start=2015-05-31&end=2015-06-07&unmonitored=false (there will be another call without the start and end dates). Click on that result and go to the Response tab and hastebin the response (it could be a couple thousand lines long).