You can point the program to your log files and specify custom time range in Profile Properties > Time Range (this setting is available in the Standard, Professional and Enterprise editions).
The Enterprise edition also supports dynamic HTML reports that allow you to view statistics on any date range without need to regenerate reports, you can view a sample of such report here.
The Enterprise edition also supports dynamic HTML reports that allow you to view statistics on any date range without need to regenerate reports, you can view a sample of such report here.