Daylight Saving Time seems to serve three major purposes:
- Health: keeping sunrise roughly constant relative to when work or school starts makes modern routines easier on our circadian rhythms, improving our pyschological health and perhaps also our physical health. In addition, the daylight "saved" by not "sleeping in" hours past sunrise during the summer makes more outdoor activity possible, increasing the amount of exercise we get without conscious effort.
- Energy use: By using less artificial light and spending less time inside watching TV during the summer, America saves about 1% on total energy use by using Daylight Saving Time.
- Safety: Daylight Saving Time tries to keep both morning and evening commutes in daylight when possible. But when that isn't possible, it tries to ensure that at least the morning commute is during daylight. This reduces car-accident injuries by thousands or tens of thousands per year.
I think a time system could improve health, energy use, and safety even more if it were to make small adjustments throughout the year instead of large adjustments twice a year. For example, a small amount of time might be added or taken away just before 2am every morning, in order to keep sunrises at 6am at a latitude of 40 degrees. The daily changes would be small enough for most people to ignore -- less than two minutes per day even around the equinoxes.
Interestingly, switching to continuous time change would also address the main criticisms of DST:
- Lost productivity and an increase in fatal auto accidents twice a year due to disruption of sleeping patterns.
- Lost productivity fiddling with clocks.
- Farmers are forced out of synchronization with the rest of society.
It seems like my favorite kind of compromise, one that reveals a false trade-off and makes both sides happier than they would have been with their previous preferred solutions.
Of course, there would be new drawbacks. Certain time calculations would be more difficult: night-shift workers might find themselves needing to keep track of the changing length of each day, instead of being confused only twice a year. Planning a weekly meeting involving people in different hemispheres (or DST regimes) would become more difficult, especially if people on each hemisphere have tight schedules.
We would also have to replace our clocks and watches. I'm not about to pretend that forcing everyone to purchase new clocks would be a good thing by itself, but at least it would only be a one-time cost; computing power is cheap enough that the the price of clocks would not increase permanently. When we upgrade our clocks to deal with days that vary slightly in length, we should also give them all the ability to update themselves; this would be more pleasant than requiring you to enter the date in addition to the time after each power outage. We could also dramatically improve the user interfaces of most alarm clocks with respect to how often they fail to wake people up, but that's the subject for another blog post.
This "Continuous DST" proposal is not to be confused with the proposal known as "Year-round DST". The advantages of DST arise from the twice-yearly changes to our clocks corresponding to the changes in the seasons. While "year-round DST" might make sense as a short-term response to an energy crisis such as World War II, in the long term it equivalent to not having DST at all: over a period of several years, everyone will shift their hours back to when they are comfortable being awake unless the government also legislates working hours, store hours, and prime-time television.
I'll admit to being atypical when it comes to sleeping schedules. I work from home and can keep almost any schedule I want. I tend to be most productive at nights, when there are few distractions, so I often sleep during the day. I prefer to be outside during the evening and night, when I don't have to wear sunglasses. (As an added bonus, when I go grocery shopping, my dairy products will take less damage from the walk home). On the other hand, in college, when many students wouldn't even consider taking a class before 10am, I didn't mind having an 8am MWF class as long as I also had a 8:10am class on Tuesday and Thursday.
I'm sure many readers do keep "normal hours", whether by coercion or choice, so what do you think of Continuous DST?