A calendar heatmap visualizes date-based data using the structure of a calendar. Each day is represented by a cell, and color intensity shows the value for that day. It is useful for seeing daily activity, frequency, seasonality, and weekly patterns.

Use Cases

• Contribution or activity logs
• Daily sales or traffic
• Habit tracking
• Weather or environmental daily values

Design Notes

• Make the calendar orientation clear.
• Use a color scale suited to the data.
• Label months and weekdays.
• Consider missing days and holidays.

Summary

Calendar heatmaps are effective when the calendar structure itself matters. They reveal daily and seasonal patterns that ordinary line charts may hide.