It's the category axis which needs ordering not the series. So you just need to add:
x.addGroupOrderRule(["January 2012", "January 2013"]);
Here's the fiddle: http://jsfiddle.net/gcu2Y/1/
Question
I can't get the chart categories to match the legend. Maybe my data could be laid out better? Items should sort based on Date inside of each category.
Please see Fiddle here: http://jsfiddle.net/gcu2Y/
Using the addOrderRule doesn't seem to be working.
s1.addOrderRule(["January 2012", "January 2013"]);
Thanks!
La solution
It's the category axis which needs ordering not the series. So you just need to add:
x.addGroupOrderRule(["January 2012", "January 2013"]);
Here's the fiddle: http://jsfiddle.net/gcu2Y/1/