Hi Bob,
This may be an issue with the values and the corresponding date time – actually the grouping.
You can try to add Sorting in the Pivot >> Data Groupings >> Categories >> Sorting. Something like:Expression: =Fields!Time_Stamp.ValueDirection: Ascending
Let us know if this helps.
PS - there was no screenshot with your post, please try to attach it again.
Best Regards,Nevron Support Team
Most likely this is because the data in "Date" field is not recognized as DateTime values. Probably you have an Excel spreadsheet and use the Excel Services connection. By using the DATETIME function you should be able to convert to DateTime value. The date time is parsed according to the specified culture. If culture is not specified the value is parsed with the current thread culture. Check out the DateTime.TryParse documentation in MSDN for a complete discussion.
Regarding setting the X axis as range of dates, can you please elaborate.The following KB topic describes how you can filter the chart based on a begin and end date: http://support.nevron.com/KB/a206/filter-the-chart-web-part-based-on-begin-and-end-date.aspx