In addition to what Joquer posted you have to make sure you are set up right too.
At one point we changed the setup to include another guild but we no longer do that. If you go to your set up tab ensure you have automatic selected, then hit Connet (or whatever the button is called) Wait the two minutes for it to synch and you should be set.
Every time you log on the calendar mod will have to synch with the guild again so to ensure you get all the info on the guild channel make sure you wait the two minutes before you use the calendar.
I haven't had any issues with the mod, but I do play a lot during the day and I synch with most people daily.