dth  = 620,
      svgHeight = 300,
      margin = { top: 20, right: 40, bottom: 60, left: 40 },
      chartWidth  = svgWidth  - margin.left - margin.right,
      chartHeight = svgHeight - margin.top  - margin.bottom;

  var x = d3.scaleTime().range([0, chartWidth])
            .domain(d3.extent(data, function (d) { return d.date; })),
      y = d3.scaleLinear().range([chartHeight, 0])
            .domain([0, d3.max(data, function (d) { return d.p90; })]);

  var xAxis = d3.axisBottom(x)
                .tic