I love the reputation graph; it's fun to track my reputation over time and helpful to see a visual representation of which questions and answers users have found most useful. One thing that seems like a bug to me is that when you first click to the rep graph, the listed end date is always today's date, even if I didn't receive any reputation today. The graph itself gets this right, with the right edge of the graph corresponding to the most recent day my reputation changed. But to see what day that actually was, I have to click in the graph and drag past the right end of the graph. Then the value for "end date" changes to the real date of my last rep change.
It may be too computationally expensive to implement a change this frivolous, but would it be possible to show the "real" end date in the text field by default, rather than today's date?