Rule of thumb - post thoughts a few days after you attend an event. Usually, you will end up not posting at all.
If you volunteer at offseasons or are on the planning committee for one, you will realize that, well, s*%t happens.
I've been at plenty of offseasons in which things need to be changed/adjusted, and you kind of just roll with it. Yes, you are paying $300 for an event, but keep things in perspective here.
Shoot some constructive comments to Dan (MysterE). From his previous posts it seems the date change was not "last minute" and was also out of their control. He posted about it on 8/4/15.
Dan seems like a good guy trying to do well by his students and his community, cut him some slack and offer up support for next time.