old_contents: 
  import pytz
  
  TIMEZONE_CHOICES = zip(pytz.all_timezones, pytz.all_timezones)
  
new_contents: 
  import pytz
  
  TIMEZONE_CHOICES = zip(pytz.common_timezones, pytz.common_timezones)
  
subject: Use common timezones and not all timezones pytz provides.