GitHub-Style Calendar Heatmaps in Google Sheets

I recently came across Leila Clark's "focusd" page using a GitHub-style heatmap to track deep work time. I really like the approach, because I think habits like "spend more time focused" shouldn't be dichotomized.

I wanted to add this to my current habit-tracking Google Sheet. I made a sheet for the data, and one for the heatmaps. For the latter, I set up the basic grid, added conditional formatting for the heatmap, and a formula that sums up the relevant values from the data sheet.

ChatGPT almost got it right (I only needed to add sheet references and fix one or two wrong refs), here's the full thing: =SUMIFS(TimeLog!$B$2:$B, TimeLog!$C$2:$C, $A$11, ARRAYFORMULA(TEXT(TimeLog!$A$2:$A, "ddd")), $A12, ARRAYFORMULA(WEEKNUM(TimeLog!$A$2:$A, 2)), B$11)

This will break in 2025, but by then I will hopefully either have stopped using it or come up with a fancier solution.