I am using v3.3.1 and Faker::Address.time_zone returns Atlantic/Cabo_Verde but https://api.rubyonrails.org/classes/ActiveSupport/TimeZone.html list does not contain it.

I think there is a typo and it should be Atlantic/Cape_Verde

Those naming changes are made to be consistent with the new naming of the country, ( #2848 ) however, rails does not support new naming in timezone.