OK, I tried to install the TimeZone user field, under the Miscellaneous Information category, but it doesn't appear. To test functionality, I added the First Name and Last Name fields to the Contact Information Category. They show up OK.
I also see a message when trying to add the TimeZone field.
"Another record with the same field name existed in the database record. Please choose another field name."
When I look at my DB user_fields table, I see only the 'First Name' and 'Last Name' records.
Just FYI, this is a recently upgraded install from V7.xx to V9