Campaigns - Report Summary - Email Opens by Time: No Date Time details shown!

Campaigns - Report Summary - Email Opens by Time: No Date Time details shown!

The Report Summary used to show Date/Time along the bottom axis. It no longer does this. This renders it next to useless, especially as the scale changes over time from minutes to hours to days.

Is there any other way to find out Opens by Time details. It is important part  of evaluating the effectiveness of different send times.