categoryAxis.baseUnitStep Number|String (default: 1)

The step (interval) between categories in base units. Setting it to "auto" will set the step to such value that the total number of categories does not exceed categoryAxis.maxDateGroups.

This option is ignored if categoryAxis.baseUnit is set to "fit".

<div id="chart"></div>
    categoryAxis: {
        categories: [
            new Date("2012/02/01 00:00:00"),
            new Date("2012/02/02 00:00:00"),
            new Date("2012/02/20 00:00:00")
        baseUnitStep: "3" // Displays a category for every 3 days.
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