When merging data into an Illustrator file to create a batch of bar graphs based on a group of CSV files, numerical dates merge into the graph data as numbers with decimals instead of dates. A 6/30/16 date merges into Illustrator as 6.00 and 12/31/16 becomes 12.00, so every date with the same month appears the same. This also messes up the graph, leaving the chart with two categories instead of one of the data columns being assigned to the x-axis.

This includes when dates are formatted (in Excel) as text, and when the dates include hyphens or periods instead of slashes, but the process works properly when the dates are formatted (in Excel) as dates but use the spelled-out format (ex. June 30, 2017).

We have run through a detailed discussion on the forums here, including step-by-step process with screenshots: https://forums.adobe.com/message/10573090. The end result appears to be an outside script, which is an unfortunate workaround solution to what appears to be a bug within the program.