Twice a year, once in the spring and once in the fall, we move our clocks either forwards or backwards to accommodate the change in Daylight Savings Time.
And twice a year, there are the requisite news articles written about Daylight Savings Time, explaining to everyone why we go through all this hassle. Then there are the cutesy and often misguided Facebook posts with statements like: "only the government would believe that you could cut a foot off the top of a blanket, sew it to the bottom, and have a longer blanket." (which is what prompted me to write this particular article in the first place!)
So let's get to the bottom of what Daylight Savings really is. First of all, however, we have to understand what midnight is. That's right: midnight, the time that we've decided each day should start.
Technically, midnight is the time that is halfway between sunset and sunrise. It's simple enough, but that definition needs some clarification. As the Earth revolves around the Sun, the Earth's tilt causes daylight hours to shift with the seasons.
A better definition is that midnight is the time that is halfway between sunset and sunrise, at the equator, on either the fall or spring equinox (the only two days of the year when the sun is directly overhead at the equator).
Now we're getting somewhere, but there's one more wrinkle in this definition.
You see, the Earth is just over 24,000 miles around and there are 24 time zones, each time zone being about 1,000 miles wide at the equator (ok, to be precise, the circumference of the Earth is 24,901.55 miles at the equator – but let's call it 24,000 miles for this exercise).
Since our system of measuring time is based on assigning the same time to the entire area in each of these "Time Zones", we have one more problem: midnight is really only midnight at the center of each time zone! If you move 500 miles in either direction (on average, as the time zone boundaries are adjusted to accommodate population densities as well as geographic and political boundaries), you will find that midnight is a half hour off. As you step over the line from one time zone to another, a movement of just a few feet, you suddenly go from midnight being a half hour off in one direction to midnight being a half hour off in the other direction.
Ok, we have it figured out – midnight is the time that is halfway between sunset and sunrise at the equator, on either the fall or spring equinox, at the center of the particular time zone that you are in.
But what does that have to do with Daylight Savings Time?
Historically, our typical work day would begin based on when the sun rose – our population mostly labored on farms or in similar activities that were not "time sensitive". Our workday would start at different times throughout the year; earlier in the summertime (when there is usually more work to do on a farm anyway) and later in the wintertime.
As we moved to being industrialized economies in the 1800's, the time of day we went to work started to matter a bit more. A factory couldn't operate if half the people hadn't shown up yet, so a set time of when to report to work was adopted. Trains and boats needed to run on a schedule so passengers would know when to show up at the station or dock. We became more reliant on keeping time, and it's all based on starting the day at that fixed point we call "midnight".
However, the seasonality of the axis tilt of the Earth still lengthens and shortens the daylight hours, and it varies greatly depending on how far you are from the equator ... there is very little seasonality change in the tropics, and you have extreme changes as you get closer to either the north or the south pole.
What Daylight Savings Time does, is it gives us more "usable daylight" during the summer by effectively shifting our definition of midnight to be an hour earlier. Since the typical start time of our workday stays constant all year long, 8 or 9am for the vast majority of people, we can take advantage of a later sunset – shifting an hour of daylight from early morning (when we'd all still be sleeping) to evening time, when we are still awake. Initially, this change was instituted to save power – which it does ... we get up at the same time of the morning either way, but during the summer the sun sets around 9pm on average with Daylight Savings Time, instead of 8pm without it (depending on how far north or south you are).
We could, however, get the same overall effect by shifting our work day, let's say that we all report to work at 7am in the summertime and 8am in the wintertime. The only difference is psychological. Seven am just sounds a lot earlier – no one wants to be at work at seven!
Admittedly, using a set one hour shift for Daylight Savings Time is a bit of an arbitrary thing; as you move east and west throughout a time zone you will find that sunrise and sunset will move up to a half hour anyway (based on this fixed "midnight" that we've adopted), and as you move north and south you will find that the seasonality change will move sunrise and sunset by many hours. It's a gradual change in both axis. A fixed one hour time period is just convenient.
There are proponents of making Daylight Savings Time the standard all year long – basically moving midnight to be an hour earlier throughout the entire year. The idea here is that during the winter we get up while it's dark and go to bed while it's dark – so there is no difference in energy consumption either way during the winter and we'd still get the energy savings and later sunset during the summer.
While this is quite true, we'd also get the exact same effect by scrapping Daylight Savings Time altogether and just having everyone's workday start an hour earlier throughout the year, as suggested above. If everyone started work at 7am instead of 8am, we moved the "News at 11" show to come on at 10pm, and just did pretty much everything we do an hour earlier than we do now, it would be exactly the same as enabling Daylight Savings Time all year long.
And midnight would stay in the middle of the night, where it's supposed to be!