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How to Read It

The "Heatmap Calendar" layout is a structured heatmap that is designed to reveal periodicities: years, months, day of week, hour of day.

The layout is comprised of two nested grids. Each year of data is arranged in a row and horizontally grouped into 12 blocks, one for each month. This is the outer grid. Months are organised by an inner grid, where data is arranged in seven columns for the days of week and 24 rows for the hours of day. Weekdays are aggregated so that e.g. all Mondays of a particular month end up in the same column.

Colour is a measure of relative intensity: grey → green → yellow → red. A subtle light grey strip highlights the most active hours of the day across the entire period.

Note that all times are in UTC – unfortunately don't store a timezone for each scrobble.

Going back to the excerpt shown at the beginning:

  • We can clearly see twelve bright blocks of time, one for each month.
  • This person rarely listens to music before 10:00 UTC, or after 23:00 UTC.
  • There are two highlighted light grey strips, corresponding to the hours of day with the most activity: one during the day, and one in the late evening. (This is most visible in the early months to the left.)
  • In most months there is a clearly visible lunch break. In the summer months this is around 12:00 UTC, in the winter around 13:00 UTC. This change is most likely an artefact of daylight saving time.
  • The well-structured routine appears to break up in December, which may indicate a travel period.