A circular calendar visualization arranges the days of the year as concentric arcs, with each month represented by a colored ring segment and individual day cells marked within. The example plots specific project dates—marked with distinct colors and symbols—onto this radial timeline, while the current day is highlighted as a special point. Built with D3 v4, the code uses `d3.arc` to draw the arcs, `Date.prototype.getDOY` to compute day-of-year angles, and SVG paths for rendering. The underlying data is a small hardcoded array of date–project pairs.