The North American Central Time Zone (CT) is a time zone in parts of Canada, the United States, Mexico, Central America, some Caribbean Islands, and part of the Eastern Pacific Ocean. Central Standard Time (CST) is six hours behind Coordinated Universal Time (UTC). During summer, most of the zone uses daylight saving time (DST), and changes to Central Daylight Time (CDT) which is five hours behind UTC. The largest city in the Central Time Zone is Mexico City; the Mexico City metropolitan area is the largest metropolitan area in the zone and in North America.