The Mountain Time Zone in the United States is UTC-7, or seven hours behind the time at the 0° Longitude, also known as the Prime Meridian. The Earth rotates 360° each 24 hours, or 15° each hour, so each 15° of longitude away from the Prime Meridian should represent one hour of time difference. The natural longitude position of the Mountain Time Zone is at 105°W, because 7 x 15 = 105. The natural boundaries of the Mountain Time Zone are 97.5°W on the east and 112.5°W on the west, because those lines, at 7.5° away from the natural line, represent the halfway points to the prior and next natural lines.
The Mountain Time Zone in the United States is UTC-7, or seven hours behind the time at the 0° Longitude, also known as the Prime Meridian. The Earth rotates 360° each 24 hours, or 15° each hour, so each 15° of longitude away from the Prime Meridian should represent one hour of time difference. The natural longitude position of the Mountain Time Zone is at 105°W, because 7 x 15 = 105. The natural boundaries of the Mountain Time Zone are 97.5°W on the east and 112.5°W on the west, because those lines, at 7.5° away from the natural line, represent the halfway points to the prior and next natural lines.
On the map, the natural midpoint line is shown, running almost directly through Denver and Cheyenne. The natural edgelines are also drawn in. The eastern edgeline is the one which runs just to the west of Fargo, Sioux Falls, Lincoln, and Dallas. Similarly, the natural western edge of the UTC-7 time zone is the line which passes west of Helena, Idaho Falls, and Salt Lake City. Overlaid on these natural lines are the actual boundaries of the Mountain Time Zone. What it illustrates is just how much of territory is in the wrong time zone. Most of Idaho, including Boise, Twin Falls, and Sun Valley, belongs in the Pacific Time Zone. As it stands, only the northern half of Idaho's panhandle is in the Pacific Time Zone. Similarly, most of the land in Texas, including the cities of Austin, San Antonio, Lubbock, Amarillo, and Midland/Odessa, belongs in the Mountain Time Zone, even though the current boundaries include only El Paso. Nearly the entire states of North Dakota, South Dakota, and Nebraska, most of Kansas, half of Oklahoma, and a giant chunk of Texas should rightfully be in the Mountain Time Zone, but have ended up in the Central Time Zone, thus making it one hour later than it should be in all of these wrong-time-zone places. The sunrise time is one hour later than it should be as is the hourof sunset. Why is this? There probably isn't a single answer, but generally, the answer is that there are more considerations than just geography. The desire to coordinate clocks around other boundaries is probably the single biggest reason. State lines, which of course are often arbitrary lines themselves, often dictate that the natural time zone boundaries should be ignored in favor of keeping all or most of the state's population within the same time zone. It just makes sense. The natural boundary of the Mountain Time Zone cleaves the western third of Utah from the rest of the state, and, even worse, if the natural boundary were used, Arizona would be cut in half. In fact, the situtaion in Arizona really highlights the problem: the natural boundary crosses through the Valley of Sun somewhere around 207th Avenue, just 25 miles west of downtown Phoenix. Placing the time zone boundary there would place the far western suburbs of Maricopa County into a different time zone than downtown Phoenix Of course, Even if Buckeye, were moved into the Pacific Time Zone, it's likely that many residents would keep their clocks synchronized with the time in Phoenix to avoind being late to work, school, and other appointments. Effctively, in these western suburbs, there would be a de-facto adoption of Mountain Time anyway. That's why it just makes sense for the state to keep everybody in the same time zone. Indeed, a poiulation which shares common economic and social ties is even a stronger reason to choose to violate the natural boundaries. As a state, Idaho has chosen to be split for this reason. Kellogg, Idaho, is actually further east than Boise, albeit only slightly. Nevertheless, Kellogg observes Pacific Time while Boise is on Mountain Time. It is one hour earlier in Kellogg than in Boise, even though the capital city is further west. This is because Kellogg is in the panhandle, and Kellogg, and the rest of the panhandle are more integrated with Spokane and areas of neighboring eastern Washington than it is with the rest of its own state. For the same reason, Boise pulls two counties from next-door Oregon into its Mountain Time Zone sphere. So the answers for why places are in the wrong time zone are varied, but at the same time thet are understandable with a little examination. The thing that I find the most interesting is how often a wrong time example turns out to be in one direction. Nearly always, therse wrong time zone examples skew eastward; that is, they tend to create situations where the clocks are one hour later than they should be, rather than earlier. I suppose that illustrates that people prefer later sunrises and later sunsets. Perhaps, that's a topic to explore in another essay.
©2023 Dan Stober
Created 2022-06-05
Last updated 2023-03-03