what you most likely need is plotbands

xaxis.plotbands

a colored band stretching across the plot area marking an interval on the axis.

in a gauge, a plot band on the y axis (value axis) will stretch along the perimiter of the gauge.

plotbands can be added on either of the axes, in your case you seem to want it on the xaxis, following is how one could do it

xaxis: {
    plotbands: [{ 
        color: '#fcffc5',
        from: date.utc(2010, 0, 2),
        to: date.utc(2010, 0, 4)
    }]     
}

plotbands @ jsfiddle