A circular calendar displays a full year of events as colored arcs arranged in concentric rings, with each ring representing a month and event labels positioned along the outer edge. The visualization uses d3.arc to draw the arcs, d3.select to manage the SVG, and custom date prototype methods to calculate day-of-year values that map to angular positions. Event data is defined in a JavaScript array with start and end dates, while CSS classes control the color scheme for each month and event type. The layout also includes hover effects on event arcs to highlight interactions.