Daylight Savings Time: the science and ‘sensibility’ behind it

Scott Sutherland
GeekquinoxNovember 3, 2012

It's that time of year again. Except for Saskatchewan and a few small regions scattered across the country, when Saturday ends and Sunday starts — specifically at 2 a.m. on Sunday, Nov. 4 — the clocks shift back one hour as Daylight Savings Time ends. It means you are waking up this Sunday morning after an extra hour of sleep (or whatever you have planned), but why do we do this every year?

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If you're not fond of the whole concept, I don't know if it will help, but there is some science behind it all.

The axis of Earth's rotation — its 'axial tilt' — is tilted by just over 23 degrees. It maintains this same angle throughout its entire orbit around the Sun, so that at the winter solstice, the northern hemisphere is tilted away from the Sun, and at the summer solstice the northern hemisphere is tilted towards the Sun. In between, at the vernal (spring) and autumnal (fall) equinoxes, there is a short amount of time when the Earth is titled neither towards nor away from the Sun.

For us in Canada, that means that most of the major cities in the country get about 16 hours of daylight at the start of summer, roughly 12 hours of sunlight when spring and fall begin, and only about eight hours of sunlight when winter starts.

There's not too much we can do in the winter to extend the number of useful hours of daylight we have available to us. Shifting the clock either way then would just cut into that number. However, in the summer, with several of those daylight hours happening while most people are still in bed (with sunrise as early as 5 a.m. local time). Therefore, shifting our clocks so that we 'spring forward' puts that earliest sunrise at around 6 a.m., and it gives us that extra hour at the end of our day.

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Part of the reason for this is economical. It benefits most businesses to have more daylight hours at the end of the day, so that people will feel more inclined to go out (or stay out) shopping. There are also supposed to be benefits in lower electricity costs, fewer traffic accidents, reduced crime and increased physical and psychological health. However, there is no conclusive evidence for any of these, either due to the many conflicting reports and studies that have been done on the subject, or due to negative effects that equal or outweigh any positive effects.

For example, switching the clocks back and forth has been found to have a profoundly negative effect on our circadian rhythms — how our bodies regulate by the cycle of day and night — affecting us for weeks afterwards. This can offset any benefit of more sunlight later in the day, causing an overall negative effect on our health and possibly resulting in more traffic accidents. Another example is energy consumption, which has seen studies both support and refute the idea that we save more energy by making the switch to Daylight Savings Time each year.

There has been some talk of switching to Daylight Savings Time permanently, effectively making DST the new 'standard' time (I have advocated this, myself). A few countries have already done this, such as Russia, Iceland and Belarus. Given that the majority of the world's countries either no longer observe DST, or have never observed it, and that 'permanent' DST may actually be a detriment in the winter, it might be more beneficial to simply abolish the practice altogether, keeping us on 'standard' time permanently.

With the world becoming more interconnected, and our schedules shifting accordingly, the concept of Daylight Savings Time may be a bit outdated these days. I'm not sure it would really help, but with so much uncertainty about whether or not it actually does us any good, perhaps it's time to consider ending it once and for all.