During setup of a DotNetNuke portal the application asks for a time zone.  In the drop down list "Arizona Time Zone" is not listed as an option. After searching the internet I located an article on DotNetNuke forum suggesting "(UTC -07:00) Mountain Time". http://www.dotnetnuke.com/Community/Forums/tabid/795/ctl/ContentRemoved/mid/2108/Default.aspx. This bookmark has been removed from DotNetNuke forum.

I did some research and located the following article of users complaining about "Arizona Time Zone" not an option.

http://www.codeplex.com/dnn/WorkItem/View.aspx?WorkItemId=12574
"Every place I've seen a list of time zones lacks an entry for Arizona. There is Mountain time, but no Mountain Standard time. Everyone else plays with their clocks twice a year (daylight savings), but Arizona remains constant. Will you please take Arizona's time zone into account by adding an entry for MST?"

The following Microsoft article suggests "(UTC -07:00) Mountain Time"

http://msdn.microsoft.com/en-us/library/ms870470%28EXCHG.65%29.aspx

On the following Arizona state DotNetNuke website the default time zone is "(UTC -07:00) Mountain Time."

http://www.dnnsupremecourt.state.az.us/Home/tabid/36/ctl/Register/Default.aspx

In conclusion I believe for DotNetNuke users in Arizona the correct time zone is "(UTC -07:00) Mountain Time" for the above suggested reasons and after setting a portal located in Arizona to this time zone I have not seen any issues.