We have different time zones because the Earth is a sphere and rotates on its axis once every 24 hours. As the Earth rotates, different parts of the Earth are exposed to the sun’s light at different times.

If we all used the same time zone, it would be noon in some places when it was midnight in others. This would make it difficult to coordinate activities and communicate with people in other parts of the world.

Time zones are used to divide the Earth into 24 equal parts, each of which is one hour ahead of the next. This way, everyone in a particular time zone experiences the same time of day.

The time zones are based on the Prime Meridian, which is an imaginary line that runs through Greenwich, England. The time zone that is directly east of the Prime Meridian is called Greenwich Mean Time (GMT). All other time zones are defined with reference to GMT.

For example, Pacific Standard Time (PST) is 8 hours behind GMT. This means that when it is 12:00 noon in GMT, it is 4:00 AM in PST.

Time zones are not always perfectly aligned with the Prime Meridian. This is because some countries and territories have chosen to have their own time zones for reasons such as convenience or historical tradition.

For example, India is 5.5 hours ahead of GMT, even though it is located east of the Prime Meridian. This is because India adopted a time zone that was convenient for its national railway system.

Time zones can also be adjusted for daylight saving time. Daylight saving time is a system that moves clocks forward one hour in the spring and back one hour in the fall. This is done to take advantage of the longer days in the summer and save energy.

Not all countries observe daylight saving time. Some countries, such as China, do not observe daylight saving time at all. Others, such as India, only observe daylight saving time in certain parts of the country.