code: function buildAxis(){
              let minor, major;
  
              if (xAxisFormat === 'custom' && typeof xAxisCustomFormat === 'string') {
                  minor = {
                      tick: xTicks,
                      format: d3TimeFormat.timeFormat(xAxisCustomFormat)
                  };
              } else {
                  ({minor, major} = timeAxisHelper.getTimeSeriesAxis(data, width, xAxisFormat));
              }
  
              xAxis = d3Axis.axisBottom(xScale)
                  .ticks(minor.tick)
                  .tickSize(10, 0)
                  .tickPadding([tickPadding])
                  .tickFormat(minor.format);
          }
docs: Creates the d3 x axis, setting orientation
  @private