Final answer:
Time zones are designed to divide the Earth into slices of 15 degrees longitude each, correlating with one-hour differences. Practical deviations occur, with some countries like India using half-zones, and others like China using a single time zone across the country.
Step-by-step explanation:
The time zones across the world are designed to divide the planet into slices of longitudes, each theoretically covering 15 degrees, correlating with one hour of time difference. However, practical applications differ due to geographical, political, or social reasons. For instance, the continental United States includes four primary time zones - Eastern, Central, Mountain, and Pacific - which do not strictly adhere to 15-degree longitude slices. This inconsistency can cause some time zones to divide and zigzag to align with state lines, or in the case of China, the entire country operates on a single time zone despite its vast land area.
The initial concept for time zoning was to organize the slices such that the sun would roughly be overhead at noon in every zone following the 15-degree rule. However, some countries like India and China have deviated from this standard system, with India adopting a half-time zone (UTC+5.5) and China using only one time zone for the entire country. This system ensures that all places within the same zone keep the same standard time, which simplifies coordination and communication across different regions.