Bar chart with only a single month of data doesn't seem to respect date for

IfIf my DataSeries is spread over multiple months then everything works as expected, however if all the data is within a single month it displays a weird x axis label. My code is:

configuration.getxAxis().setType(AxisType.DATETIME);
configuration.getxAxis().setDateTimeLabelFormats(new DateTimeLabelFormats("%b %Y", "%Y")); 

I’ve attached a screenshot to show what I mean. For that chart I have 3 items in the DataSeries, all for the month of Jan 2018. The format I’d like is Jan 2018 on the x-axis
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