I created an event called "Horse Event" for 3 days

I created an event called "Horse Event" for 3 days in September, but when you want to click through in the sidebar widget http://www.itrainmyhorsesbrain.com/forums/overview/, you can only click to the next month. From there on the widget loses where to go and points back to the year before (http://www.itrainmyhorsesbrain.com/agenda/2012/), which obviously doesn't exist.
The event itself does exist: http://www.itrainmyhorsesbrain.com/agenda/2013/09/1959/