Sets or returns the display type for the data on the category axis.
The display type of the axis determines how the axis will be scaled. If the DisplayType is set to Category, then each data point will have an equal amount of horizontal space in Excel. This is the default in Excel when there is no category data explicitly set for the chart, or when the category data is set to any values other than dates.
If the DisplayType is set to TimeScale, then the category axis will show a range of dates, and data points may not be evenly distributed. This is the default in Excel for charts whose category data is set to a set of dates. This display type also allows you to specify the interval in units of time that labels should appear on the category axis, via the MajorUnit, MajorUnitValue, MinorUnit, MinorUnitValue, and [BaseUnit] properties. It also allows you to specify the range of dates that will be displayed via the MinimumValueAsDate and MaximumValueAsDate properties.
If the DisplayType is set to Automatic, then Excel will automatically choose one of the DisplayTypes, depending on the current category data. This is the default for all newly created charts, both in Excel and in ExcelWriter.