I looked at the dojo and it looked good, but your data starts toward the end of the month. If the first date is January 1st, 2015 and the date step is 30, the first date displayed on the axis is 01/2015 (for 1/1/2015), the second date would be 01/2015 (for 1/31/2015) and the third would be 03/2015 (for 3/2/2015 thirty days later completely skipping the 28 days in February). I modified the date values - attached is a screen shot.
In another case, if we were starting with Oct 1st, the first date would be 10/year, the second would be 10/year and the third would be 11/year. while the labels are accurate, the labels appear at the end of the month/span instead of the beginning.