I have tried this plugin with several sites. When it works it is great. But it either breaks when WordPress upgrades, or it breaks when the developers upgrade the plugin. There are also different versions of it available from the WordPress plugin directory and the developer's web site so it's hard to keep it up to date.
3.9 broke it again and I have one other web site where Bing Bot got lost in the calendar and just kept hammering it until my ISP reported the client was almost hitting their bandwidth limit. This for a client that has never been close to their limit before.
I'm going to be removing it from all of my client's sites and try a different calendar.
Too bad, because I liked how it worked when it did work.