Add this to your dashboard. You can change to any screenname. It shows the most popular and distribution of the timezones of your followers.If you want to track this over time, we also offer tracker workbooks that keep data on your computer.

Name: twitter followers by time zone for any twitter user.xlsx.xlsx 
Subject: widget 
Keywords: twitter the time zones of of followers

This widget is available for Excel 2007 and above and is refreshed with Next Analytics.