This example presents a calendar-style grid mapping days of the month on the y-axis against hours on the x-axis for January 2017. Each hour-cell is rendered as a small SVG rectangle, with tooltips revealing the date and hour. The code uses D3 v4’s `d3.timeHours` to generate the hourly intervals and `d3.timeFormat` to label data, storing formatted strings via `.datum()`. The layout is fixed at 900 by 900 pixels, with cells sized at 17 pixels and axes labeled generically (“xxx”), suggesting a template for time-series exploration.