I have a job for which Jenkins shows two trend charts: one for warnings (from warnings-ng-plugin) and another for test results (I think from junit-plugin). When I click the gear button at the top right corner of the warnings trend chart, the "Configure trend chart" popup has a "General configuration" section with these radio buttons in it:

• "Show results per build (x-axis: build number)"; initially selected.
• "Show aggregated results per day (x-axis: day of build)"

I select "Show aggregated results per day (x-axis: day of build)", and click "Save". Both trend charts change to show dates rather than build numbers. That's a bit surprising but okay.

I then click the gear button at the top right corner of the test results trend chart. That opens a similar "Configure trend chart" popup, although not identical. This again has the same two radio buttons, but now neither radio button is selected. That's a bug; the "Show aggregated results per day (x-axis: day of build)" radio button should be selected because that's what the trend chart is showing.