Question

what is the purpose of having time zones

Answer 1

The Greenwich Meridian, also known as the prime meridian or International Meridian, is the "starting point" for dividing the Earth's surface into time zones. Each time zone is 15 degrees of longitude wide (with local variations) and the local time is one hour earlier than the zone immediately to the east on the map.

Answer 2

time zone is the region of the global that observed a uniform standard tume for legal commercial and social purposes