A Calendar Chart renders date-indexed data as a day-cell grid, revealing activity rhythms and long-term trends at a glance. It works especially well for contribution logs, habit tracking, and any metric recorded daily over multiple years.
This sample charts the GitHub contributions of Mike Bostock, co-creator of D3.js and Observable, from 2017 to 2021. A dark background with purple ordinal color levels, reversed year order, custom title styling, and contribution-count tooltips give it a polished, branded look.
Follow the step-by-step Calendar Chart Tutorial to learn how this chart was built. See the Calendar Chart documentation for all configuration options.