When panning on a XYPlot which domain axis is a PeriodAxis which autoRangeTimePeriod is Day, the axis range will expand one day after each call to PeriodAxis.pan(). As a result, panning the chart seems weird. The effect gets even worse when the chart is zoomed in.
I found that it was caused by rounding the adjusted lower bound and upper of the range each time the pan() method is called. For the moment I overrided PeriodAxis, use two variables to hold the double value of lower and upper bound and modify the pan() method to use the double values instead of the rounded long values.