How many states are in the central time zone? Write their full names.
central time zone refers to time_zone = 'Central'
SELECT SUM(CASE WHEN T1.time_zone = 'Central' THEN 1 ELSE 0 END) AS count FROM zip_data AS T1 INNER JOIN state AS T2 ON T2.abbreviation = T1.state WHERE T1.time_zone = 'Central'