This tests that tick marks don't break when the axis crosses into daylight savings time.
The tick marks should all be on day boundaries or nice hours (6, 12, 18), rather than on odd time boundaries like 5, 11, 17 and 23.
This chart shows a continuous line going across the "fall back" EST/EDT event. You may need to switch your computer's time zone to Eastern to see this. The x-axis tick marks go from 01:00 → 01:55 and then back to 01:00.
This chart is analogous to the first, except at a "spring forward".
This chart shows a continuous series which crosses a "spring forward". The x-axis ticks should skip from 1:55AM to 3:00AM.