There are four time zones in the U.S.

• Eastern TZ Example : Massachusetts, New York, Florida etc.
• Central TZ ( lags Eastern TZ by one hour ) Example : Iowa, Kentucky, Indiana etc.
• Mountain TZ ( lags Eastern TZ by two hours ) Example : Colorado, Utah, Wyoming etc.
• Pacific TZ ( lags Eastern TZ by three hours ) Example : California, Oregon, Washington etc.

As the name suggests, the time is set in such a way that maximum day light could be used. e.g. During summer, the sun rises at around 4-5 o'clock. So the clock is set forward by one hour. This forces all activities to start one hour earlier so that maximum day light is used till late in the evening. Therefore: The Clock is set back by one hour on the first Sunday of November 1 (Fall Season) at 2:00 am. Clock is once again set forward by one hour on the first Sunday of April at 2:00 am. (Spring Season). The easiest way to remember this is FALL BACK, SPRING AHEAD. By the way, Arizona is the only state which is not affected by daylight-saving. People there do not ever change the time in their clocks.