UT1 - UTC by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  font: 10px sans-serif;
}

.line {
  fill: none;
  stroke: #696969;
  stroke-width: 1.5px;
}

svg:not(:hover) .focus {
  display: none;
}

.focus line {
  stroke: red;
  shape-rendering: crispEdges;
}

.focus circle {
  fill: #fff;
  fill-opacity: .5;
  stroke: red;
  stroke-width: 1.5px;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.y.axis path {
  display: none;
}

.y.axis line {
  stroke: #ccc;
  stroke-dasharray: 2,3;
}

.x.axis line + text {
  stroke: #fff;
  stroke-width: 4px;
}

.overlay {
  fill: none;
  pointer-events: all;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var margin = {top: 20, right: 40, bottom: 20, left: 10},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var format = d3.format("+.1f");

var x = d3.time.scale()
    .range([0, width]);

var y = d3.scale.linear()
    .domain([-1, 1])
    .range([height, 0]);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("right")
    .tickSize(-width)
    .tickFormat(format)
    .tickPadding(6);

var line = d3.svg.line()
    .x(function(d) { return x(d[0]); })
    .y(function(d) { return y(d[1]); });

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.json("offsets.json", function(error, offsets) {
  if (error) throw error;

  var start = Date.UTC(1973, 0, 2),
      step = 1000 * 60 * 60 * 24;

  offsets = offsets.map(function(t, i) { return [new Date(start + i * step), t]; });
  x.domain([start, start + (offsets.length - 1) * step]);

  svg.append("g")
      .attr("class", "y axis")
      .attr("transform", "translate(" + width + ",0)")
      .call(yAxis);

  svg.append("path")
      .datum(offsets)
      .attr("class", "line")
      .attr("d", line);

  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + y(0) + ")")
      .call(xAxis)
    .selectAll("text")
    .select(function() { return this.parentNode.appendChild(this.cloneNode(true)); });

  var focus = svg.append("g")
      .attr("class", "focus");

  focus.append("line")
      .attr("class", "x")
      .attr("y1", y(0) - 6)
      .attr("y2", y(0) + 6);

  focus.append("line")
      .attr("class", "y")
      .attr("x1", width - 6)
      .attr("x2", width + 6);

  focus.append("circle")
      .attr("r", 3.5);

  svg.append("rect")
      .attr("class", "overlay")
      .attr("width", width)
      .attr("height", height)
      .on("mousemove", mousemove);

  function mousemove() {
    var d = offsets[Math.round((x.invert(d3.mouse(this)[0]) - start) / step)];
    focus.select("circle").attr("transform", "translate(" + x(d[0]) + "," + y(d[1]) + ")");
    focus.select(".x").attr("transform", "translate(" + x(d[0]) + ",0)");
    focus.select(".y").attr("transform", "translate(0," + y(d[1]) + ")");
    svg.selectAll(".x.axis path").style("fill-opacity", Math.random()); // XXX Chrome redraw bug
  }
});

</script>