# Welcome to the Highcharts Gantt JS (gantt) Options Reference

These pages outline the chart configuration options, and the methods and properties of Highcharts objects.

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# yAxis.dateTimeLabelFormats

For a datetime axis, the scale will automatically adjust to the appropriate unit. This member gives the default representations used for each unit. For easier data interpretation, `hour`, `day`, `month` and `year` units can be used and formatted as boundary tick values. Check boundaries map below to see where to format boundary ticks on given main time units.

        baseUnit: boundaryUnit
        ----------------------
        millisecond: 'hour',
        second: 'hour',
        minute: 'hour',
        hour: 'day',
        day: 'month',
        week: 'month',
        month: 'year',
        year: 'year'

For an overview of the date time label formats configuration, see dateFormat.

Defaults to:

    {
        millisecond: { main: '%[HMSL]' },
        second: { main: '%[HMS]' },
        minute: { main: '%[HM]' },
        hour: { main: '%[HM]', boundary: undefined },
        day: { main: '%[eb]', boundary: '%[eb]' },
        week: { main: '%[eb]' },
        month: { main: '%[bY]', boundary: undefined },
        year: { main: '%Y', boundary: undefined }
    }