USA is divided into four time zones:

Pacific Standard Time (PST): States like California, Washington, Oregon, etc., come in this zone.

Mountain Standard Time (MST): States like Utah, Colorado, Wyoming, etc., come in this zone. MST is ahead of PST by 1 hour.

Central Standard Time (CST): States like Texas, Indiana, Iowa, etc., come in this zone. CST is ahead of MST by 1 hour and PST by 2 hours.

Eastern Standard Time (EST): States like New York, Massachusetts, Florida, etc. come in this zone. EST is ahead of CST by 1 hour, MST by 2 hours and PST by 3 hours.

Daylight Saving Time:

There is no consistency in the day and night span. In USA the days are very short in winter, and very long in summers. So time is set in such a way, so as to make the maximum use of the daylight. Hence, it is so called 'Day Light Saving'. It is changed twice every year. Arizona is the only state, which is not affected by day-light-saving. People in this state do not ever change the time on their clocks. (Alaska and Hawaii)