An example using date-extract, d3js etc. Dates referenced in the DC Code.
<!DOCTYPE html>
<meta charset='utf-8'>
<style>
body {
font: 10px sans-serif;
shape-rendering: crispEdges;
}
.day {
fill: #fff;
stroke: #ccc;
}
.month {
fill: none;
stroke: #000;
stroke-width: 2px;
}
.RdYlGn .q0-11{fill:rgb(165,0,38)}
.RdYlGn .q1-11{fill:rgb(215,48,39)}
.RdYlGn .q2-11{fill:rgb(244,109,67)}
.RdYlGn .q3-11{fill:rgb(253,174,97)}
.RdYlGn .q4-11{fill:rgb(254,224,139)}
.RdYlGn .q5-11{fill:rgb(255,255,191)}
.RdYlGn .q6-11{fill:rgb(217,239,139)}
.RdYlGn .q7-11{fill:rgb(166,217,106)}
.RdYlGn .q8-11{fill:rgb(102,189,99)}
.RdYlGn .q9-11{fill:rgb(26,152,80)}
.RdYlGn .q10-11{fill:rgb(0,104,55)}
</style>
<body>
<script src='//d3js.org/d3.v3.min.js'></script>
<script>
var width = 960,
height = 136,
cellSize = 17; // cell size
var day = d3.time.format('%w'),
week = d3.time.format('%U'),
format = d3.time.format('%Y-%m-%d');
var color = d3.scale.quantile()
.range(d3.range(11).map(function(d) { return 'q' + d + '-11'; }));
var svg = d3.select('body').selectAll('svg')
.data(d3.range(1970, 2013))
.enter().append('svg')
.attr('width', width)
.attr('height', height)
.attr('class', 'RdYlGn')
.append('g')
.attr('transform', 'translate(' + ((width - cellSize * 53) / 2) + ',' + (height - cellSize * 7 - 1) + ')');
svg.append('text')
.attr('transform', 'translate(-6,' + cellSize * 3.5 + ')rotate(-90)')
.style('text-anchor', 'middle')
.text(function(d) { return d; });
var rect = svg.selectAll('.day')
.data(function(d) { return d3.time.days(new Date(d, 0, 1), new Date(d + 1, 0, 1)); })
.enter().append('rect')
.attr('class', 'day')
.attr('width', cellSize)
.attr('height', cellSize)
.attr('x', function(d) { return week(d) * cellSize; })
.attr('y', function(d) { return day(d) * cellSize; })
.datum(format);
rect.append('title')
.text(function(d) { return d; });
svg.selectAll('.month')
.data(function(d) { return d3.time.months(new Date(d, 0, 1), new Date(d + 1, 0, 1)); })
.enter().append('path')
.attr('class', 'month')
.attr('d', monthPath);
d3.json('dates_compressed.json', function(error, data) {
color.domain(d3.values(data));
rect.filter(function(d) { return d in data; })
.attr('class', function(d) { return 'day ' + color(data[d]); })
.select('title')
.text(function(d) { return d + ': ' + data[d] + ' times referenced'; });
});
function monthPath(t0) {
var t1 = new Date(t0.getFullYear(), t0.getMonth() + 1, 0),
d0 = +day(t0), w0 = +week(t0),
d1 = +day(t1), w1 = +week(t1);
return 'M' + (w0 + 1) * cellSize + ',' + d0 * cellSize
+ 'H' + w0 * cellSize + 'V' + 7 * cellSize
+ 'H' + w1 * cellSize + 'V' + (d1 + 1) * cellSize
+ 'H' + (w1 + 1) * cellSize + 'V' + 0
+ 'H' + (w0 + 1) * cellSize + 'Z';
}
d3.select(self.frameElement).style('height', '2910px');
</script>