“The color of springtime is in the flowers; the color of winter is in the imagination.”
- Terri Guillemets
‘Tis this time again. The time of year to get big wholly sweaters out and enjoy the comfort of a cosy blanket while snuggling on the sofa. ‘Tis this time of year. The time to decide when it is time to start the heating in the house and when it stops to be “too soon”. ‘Tis this time of year. The days are getting shorter, the sun doesn’t look as bright anymore and disappears by 4pm. ‘Tis this time of year. Time to change the clocks and “fall back”. Wintertime has arrived.
It is hard to complain about the wintertime change: we basically get an extra hour of sleep on a Sunday. I kinda wish every Sunday would be time-change Sunday! It is another story when Summertime change arrives and suddenly you lose a whole hour of sleep… Not too keen on this one. Recent research has also shown that it’s not great for us and our body struggle to adjust to it. Just like it struggles with jet lag.
In a time far far away, the sun itself regulated daylight activities, dividing daylight into 12 hours, regardless of actual daytime. As a result, hours had difference length between seasons, and were longer in summer than in winter. This practice was abolished in the 14th century with the establishment of equal-length civil hours.
The concept of daylight-saving time is very recent and was first suggested in the 18th century and formulated in the 19th century by a Kiwi, George Hudson. See, the good George was an entomologist in his spare time and found mostly inconvenient to not be able to look for precious specimen for the same amount of time after work throughout the year. He suggested a 2-hour shift (imagine losing 2 hours of sleep at the Summer time-change…) in order to increase after-hour (i.e., after work hour) daylight.
Couple of years later and hundreds of kilometres above, an Englishman came with the same idea: William Willett. Our good Englishman was a golfer, and similar to his Kiwi counterpart, he also valued after-hour daylight and found it futile to let Nature dictates his golfing schedule. However, it is a Canadian city that first enacted the daylight-saving time change in 1908. Germany and Austria-Hungary were the first countries to adopt it in 1916 to reduce coal use during wartime, soon followed by most others European countries. The United states waited until 1918. Many countries abandoned the daylight-saving time after the end of the war, as most saw it as a way to preserve resources in wartime: no more war, no more need to conserve resources. Right… When the second world war came around, many countries readopted the daylight saving time and was widely adopted in the 1970s a a results of the energy crisis (funny how crisis seem a good motivation for savings…).
Nowadays, most European and Americans countries follow the daylight-saving time, but it is rare in Asia and Africa. In Australia, some states follow it, while others don’t. Many countries start to question the relevance of such time-change and a recent study highlighted that it could actually be detrimental to our circadian clock, the internal clock regulating our internal biology. See, our circadian clocks use daylight to regulate our activity and sleep patterns. Humans naturally adjust to the annual change in daylight under standard time… but struggle under daylight-saving time (i.e., summer time), taking up to 6 weeks to fully adjust. The extend of the disruption to other human biological aspects has not yet been studied but this recent study shows it could have more impact than previously thought. Another argument in favour of dropping the summer time change (if losing 1 hour of sleep isn’t enough).
Those results also reflect how people suffer more from jetlag when travelling towards the east. Our circadian clock seems to be running slightly longer than 24 hours; every morning, our clock synchronise with the sun cycle and adapting our activity pattern accordingly (activity burst and down time). When travelling west, our day is longer, and the body gains the couple of extra hours it naturally longs for. However, when travelling east, your day ends up being shortened and the body struggles more to adjust.
Daylight is what is called a zeitgeber, a time-giver or synchroniser. It is an external cue that synchronise our internal biology to the natural daily light/dark cycle, throughout the seasons. But it turns out that it also has an impact on how we perceive temperatures. Another team of scientists conducted a study where they put people in a room for 30 min. The researchers could modulate the room temperature (19°C, 23°C, or 27°C), as well as the level of daylight coming into the room (low, medium, or high). After the 30 min, participants reported how they felt temperature-wise (cold or warm), but also how comfortable and acceptable they felt in such temperatures. The level of daylight entering the room did not affect how cold or warm people felt, 19°C being consistently fairly cool and 27°C fairly warm. However, low daylight level, participants perceived the cooler temperature as more uncomfortable and less acceptable than when the daylight level was high. Respectively, when the daylight level was high, the highest temperature was perceived as more uncomfortable and less acceptable. 19°C on a dim winter day feels less pleasant than on a clear summer day.
Next time you feel unpleasantly cold at home, but you think it’s still too early to turn the heating on, try turning on more lights. They don’t look as pretty as candles when snuggling on the sofa under layers of blankets, but it might help make it less uncomfortable while being economically friendly!
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