report dates not showing in order

[Caitlin_Knox]

I've created a date table, but something is wrong. On my reports, the dates do not show in chronological order. I currently have the date table column that holds the actual dates to sort ascending. From that column I parsed out the short year and month name and then merged those two columns together since the ultimate goal is to show a trailing twelve months visual- so one month will have two entries[one for the year prior]. I also tried creating a calculated column to merge the short year and month name with the same results as shown below. Its like they almost go in order, then get crazy. The earliest month in the data set is May 2015, and the most current is May 2016. So in this visualization, all data should show.