In my experience the calendar has been pretty accurate. That being said, they have published blogs recently saying that they know they've been low lately, because Disney has changed their marketing strategy over the past few years that has been doing a very good job of keeping the parks fairly well attended at all times of the year. So, overtime, TPs calendar will become more accurate. Just make sure you have your TPs electronic and use the Lines app while you're there. That way you can tweak/re-optimize them as needed on the fly. That's what we did the last two times we were there, one of which being Memorial Day weekend (VERY crowded) and our wait times were still incredibly reasonable using our TPs via the Lines app.