The Hourly Diff Delta graph helps you see how a team, or individual developer, has their productive output spread over the hours of a week. A normal Hourly Delta graph might look something like this:
Darker colors indicate higher Diff Delta during the day of week+hour combination during the date range ("Last Year")
What can we spot in regards to team productivity? In the graph above, for Alloy.dev, you can see a few phenomenon at work:
There's negligible work happening before 8am or on the weekends 👍
Wednesday -- a weekly "Work from Home" day -- doesn't glow as hot during the morning as an office day, but our team compensates for that by stretching the day longer than any office day (with the darker boxes at the bottom of the day)
Friday goes dark starting between 3-4pm, and gets very dark at 4-5pm. This is when we have our weekly company meeting.
Days are generally darker between 12-1pm -- but not much darker. Our team doesn't see much of a dropoff for lunch
This same graph can be compared to any individual developer. Here's the graph for GitClear Programmer/CEO Bill Harding over 2019:
The Hourly Diff Delta graph for a developer who's a little too wrapped up in their job (the author)
The light spots on my week (mostly Wednesday) are where the Programmer/CEO works on his emails. There is also exercise that happens between 12pm-1pm on Sunday and Wednesday, as evidenced by the lighter cells.
linkMethodology
The method that ascribes Diff Delta to each hour is wise enough to understand a commit that spans many hours applies equally across the time it was being authored. So, if you made a commit at 10am, and then at 2pm made a commit worth 100 LI, that would count as 25 LI each to 10-11am, 11-12pm, 12-1pm, and 1-2pm.