"Greenwich Mean Time ensures that the sun, on those days it is visible, is directly overhead Greenwich, England, each noon. Locales distant from England, shift UTC by a certain number of hours and minutes so that the sun is approximately overhead locally at noon. Mountain Standard Time subtracts 7 hours from UTC. We would expect 24 time zones, each corresponding to 60 minutes of longitude, but as with all things political, there are many exceptions. Nepal's time zone is 15 minutes off from India's as an expression of independence. Many locales also change the offset, advancing their clocks by one hour in the summer and turning them back in the winter, at specied days. Arizona, unlike the other states in the Mountain Time Zone, does not adopt this adjustment, called daylight saving time, presumably as an expression of independence from the federal government. The Navajo Indian reservation, located within Arizona, does use daylight saving time, perhaps to be different than Arizona. And the Hopi Indian reservation, which is completely surrounded by the Navajo Indian reservation, does not adopt daylight saving time, perhaps to differentiate themselves from the Navajos. So you can drive a few hours in Arizona and go in and out of daylight saving time four times."