 The world is divided into 24 time zones as a measurement of the Earth's rotation. Local times worldwide are based off of coordinated universal time. The prime meridian is the starting point. It's a geographical reference line that passes through Greenwich, England. To figure out local time, add one hour for every time zone east of the prime meridian, or subtract one hour for every time zone west of the prime meridian. Don't forget, there may be local variations such as daylight saving time. Subscribe to WISC Online to learn better.