See my graph to learn the answer:
http://www.swivel.com/graphs/show/15952384
To build the graph, I posted two spreadsheets:
1. List of Tech Days events and dates http://www.swivel.com/data_sets/show/1006260
2. Manually computed chart of blog entries per date
http://www.swivel.com/data_sets/show/1006263
Creating the CSV of event dates is obviously a human task. But is
there a better way to do a blog entry count in Swivel?