Time zones and Daylight Saving Time (and similar summer times in other parts of the world) are artifacts of industrialized societies imposing an arbitrary standard of measurement upon variable natural phenomena. Because the earth rotates (and the sun does not lie along its axis of rotation), every point on its surface experiences day/night cycles. A few other interesting quirks lead to the situation where the length of day varies not only with one's position between the poles, but also with the earth's position in its orbit (seasons). Not only do the length of day and night vary, but the length of the sum of day and night (one full day) varies. Tidal forces between the earth and moon and the earth and sun both slow the earth's rotation, making each day fractionally longer than the day before. While the changing length of day affects only a tiny minority of this blue marble's population, everyone living on it notices and is impacted by the variability in day/night cycles. For much of human history, the astrophysical anomalies responsible for the variation were unknown and although their effects were recognized, the functioning of society was not greatly influenced by them. In the recent geologic or distant societal past, greater dependence on mechanized timekeeping made apparent that regulating daily activities with respect to a fixed clock rather than with respect to the natural day/night cycles made for an inefficient use of sunlight. Time zones, Daylight Saving Time and other proposals were introduced to patch the discrepancy to some degree, but they have failed to satisfy, precisely because they do not acknowledge, and thus do not fix, the actual problem caused by disparity between "sun time" and a fixed clock.
Before pocket watches, and especially wristwatches, in the mid 19th century, there was little need for timekeeping more accurate than sunup, sundown, noon, or supper time. As the technology increased in accuracy, decreased in price, and increased in popularity, society (industrial, "western" society, though I'm sure the same is true elsewhere) began to take advantage of increased efficiency by scheduling ever more precisely. As rail technology improved and brought with it greater speed and availability, scheduling problems began to arise. Trains traveling from one town to the next, each town having its own local time based on the solar day, could not share the tracks without specifying not only the time any given piece of track would be used, but according to whose time it would be used. Collisions inevitably happened. Time zones were proposed as a way to fix the inevitable problems that occur when two parties with different local times (say, two train stations in adjacent cities) need to communicate, organize, and schedule common events.
Time zones were a huge improvement over every town having its own local time. Scheduling trains in a world where each town you pass through is a few minutes off versus the one before it or the one after is functionally impossible, and time zones minimized the number of corrections that needed to be made. This works quite well for trains. Even a modern high-speed train crosses time zones only once every few hours at best. Air travel begins to push the limits: the time change due to time zones is almost equal to the flight time for east-west flights. Modern telecommunications is even faster, and time zones just fall apart.
The main problem with time zones is that they do not solve the problem of two or more parties to a transaction each having different local times. Time zones are a partial solution that reduces the frequency of time changes from one per town to one per 15 degrees of longitude, more or less. Yet the ever-increasing use of telecommunications once again puts us in a position where, as a society, we routinely conduct business without a shared local time. The invention and adoption of time zones bought the US a roughly 150-year reprieve, but the partial solution is increasingly inadequate. The modern need for simple and accurate scheduling of common events among two or more parties thousands of kilometers apart routinely exposes the inefficiencies caused by time zones as meetings or conference calls or planes or other appointments are missed, even after extra time is taken to ensure correctness under a broken system.
Without a common local time, myriad problems arise. "I'll call you back in an hour" still has meaning, but "call me back by 5" becomes ambiguous. The common fix, "call me back by 5, my time", assumes that the person to make the call knows the other party's physical location and makes no error in computing the time change. If both parties were using a common time, one would say "call me by 5", to which the other might reply "I'll be asleep then. How about 1?". The problem of knowing the other party's day/night cycle remains, even in a world without time zones, but is made no worse by their removal. In fact, the situation is improved because the called party instantly knows whether 5:00 is night time, and does not have to mentally compute the other party's 5:00, correct for the time change between the two parties to arrive at his local time, decide that 6:00pm is the latest he's willing to stay at the office to take a call, and then convert that back to the first party's local time to request an alternate meeting time. Any other imaginable situation follows the same pattern: either the problem is completely removed by unified time, or it is made no worse by it. Time zones should go.
Time zones, though conceptually simple and apparently rational, hide an unspoken and nearly always unconsidered assumption that would rear its ugly head not long after time zones themselves had ceased to be controversial. The reason why time zones came into being rather than a single standard time throughout the country was the unspoken assumption that any clock standard should put sunrise roughly in the mid single-digits, AM, and sunset in the mid single-digits, PM. It seemed obvious that this is the way a clock should operate, and there was apparently no serious proposal to adopt a single time, nation-wide, even though the rail companies, which championed and used the time zone system long before governments, local or national, officially recognized it, would have benefited from the simpler system. Time zones showed that people were willing to accept a time standard in which noon did not fall precisely when the sun reached it zenith, as long as the difference was small. But the decades-long battles over Daylight Saving Time illustrate how deep-seated society's commitment is to making sure sunup and sundown fall at the right time every day. As the length of day changes throughout the year, sunrise and sunset move by several hours each, depending on latitude. But rather than accept this natural quirk of our solar system's configuration, most industrialized societies choose to adopt a scheme whereby the clock changes by an hour or so twice a year, in an effort to keep the numbers we arbitrarily assign to sunup and sundown within a narrower range.
I have read the arguments both for and against DST in the United States, either its existence at all or its extension earlier and/or later in the year. These arguments completely fail to address the fundamental problem. As a society we are conditioned to get up for a 9-5 workday. During some parts of the year, 9-5 is an inefficient time to have people working (because it's dark for part of it), so DST came into being as a way to keep the 9-5 day, but put it at a better time during the day/night cycle. For all its utility, DST is not a nationwide phenomenon. Some states observe it, some do not. Some states observe it at different times than others. Some states observe DST in part of the state but not in others. As a result, some pairs of locations share a local time during part of the year but not the rest of the year. Far from a simple patch to keep our daily activities better synchronized with the world in which we live, DST has added another unnecessary layer of complexity to what is perhaps the single most basic convention of civilization.
The simple adoption of a nationwide time standard would solve not only scheduling problems that time zones were intended to solve, but also the problem of keeping work schedules lined up with the sun. Suppose the US instituted UTC as the single official time. Then, the old 9-to-5 work day (0900-to-1700) in New York would become 0400-to-1200 (0500-1300 in the summer), and in California it would be 0100-to-0900 (0200-1000 in summer). This would seem strange for a while, but becoming comfortable with it makes the change to worldwide standard time a snap. A population used to varying work schedules (9-5 in one state, 7-3 in another) would have no problem adapting to the idea that the 6-2 workday changes to 7-3 for part of the year. No clock kludges needed. Stores particularly dependent on daylight commonly have summer hours anyway, so this change would not introduce any additional burden. Minor quirks and outright flaws with the old time system would disappear. No longer would westward-bound airplanes land at the same "time" as they took off. No longer would overnight trains on the spring edge of DST waste an hour sitting on the tracks, nor would they rush like mad to make up the lost hour in the fall, inevitably arriving at their destinations late.
Time zones are a step in the right direction, but it is long past the time to take the next step and adopt one standard time, ideally worldwide. Daylight Saving Time, on the other hand, was a bad idea from the start. Pushing business hours back by an hour for a few months out of the year to save electricity is laudable; changing local time in a horrible patchwork throughout the country is hardly the right way to go about it. Let's adopt a rational, national timekeeping standard, and then address our energy concerns separately. The two are only related by historical accident, and for the good of us all, let's separate them. The 24-hour day is a historical accident too, but one without serious detrimental consequences, so I see no reason to meddle. Time zones and DST are temporary patches whose shortcomings become clearer year by year. The solution is obvious. World-wide UTC would make the world a better place.