In the 24 hour example, not sure if it would be possible to the interval marks on the X axis centered on the hour.

For example if it is now 17h30, the graph will start at 17h31 (yesterday), but should have major vertical lines at 18h00, 19h00 etc all the way to 17h00 today. Minor tick marks could be every 15 min in between.

Not sure if that is possible, but it would look a lot better than having times that are not rounded off on the X axis.