Home > Application, Appreciation > Daylight Confusion Time

Daylight Confusion Time

I’ve always been confused by Daylight Saving Time.  It probably doesn’t help that I only really think about it twice a year.

During my recent biannual bemusement, it occured to me that one reason our approach to DST seems off to me is because it tries to compensate for a dilation with a translation.

As summer turns to winter and our part of the Earth spends less time in the sun, the length of the day contracts.  This kind of transformation is known as a dilation–a shrinking or strecthing of an object.

The yellow part of the graphs represent the amount of sunlight per day:  this part dilates, while the times-of-day on the clock stay fixed.

In order to increase the amount of productive daylight, we translate the times-of-day.  Naturally, this doesn’t change the amount of available sunlight; it simply shifts the clock-times so that more of that sunlight occurs during preferred times-of-day .

Thus, the new “day” looks like this.

So in essence, we are trying to to counteract a dilation–a transformation that changes lengths–with a translation–a tranformation that preserves lengths.

I am convinced this is at the root of my confusion about DST, although I may be the only one!

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  1. Ahmed Gouda
    November 7, 2010 at 12:57 pm

    I always saw Day Light Savings time as something farmer related. Make it so that 6 in the morning is still when the sun comes up so that they don’t “waste sunlight”.

  2. Richard
    November 26, 2010 at 3:21 pm

    Benjamin Franklin often gets credit (or blame) for inventing Daylight Saving Time (known as summer time in Europe) because he wrote an essay in 1784 suggesting that the French could save money on candles and oil by waking up earlier, thereby getting more done during daylight hours. Franklin’s essay also “suggested” ringing church bells and firing cannons at dawn to ensure that nobody would be excluded from his benevolent gesture.

  3. November 27, 2010 at 7:06 pm

    Thanks for the back-story Richard–it’s always encouraging to remember that even the giants swung and missed every now and then.

  4. Andy Huynh
    November 6, 2011 at 1:14 pm

    The change that occurs in the Fall is going from Daylight Savings time to Standard time. The change in the Spring is going from Standard time to Daylight Savings time. This means that time just got changed back to “normal” and in the Spring, the clock gets moved ahead to “save time.” What all of this means, I don’t know.

  5. November 6, 2011 at 2:16 pm

    “What all of this means, I don’t know. ”

    My sentiments exactly.

  6. November 6, 2011 at 7:38 pm

    As I understand it, the purpose of DST is to gain an extra hour of daylight during summer evenings, at the cost of an hour of daylight in the morning. This would be rational if you value daylight more in the evening than in the morning. But why not just encourage people to alter their schedules during the summer instead of adjusting the clocks? Perhaps the solution is to institute year-round Daylight Saving Time.

  7. November 6, 2011 at 11:19 pm

    What reasons do people give when arguing that an hour of daylight in the evening is more valuable than one in the morning? And yeah, if that’s the case, why not always rig it so 5-6 pm at night is always daylight?

    Certainly would make more sense for people just to alter their schedules.

  8. March 11, 2012 at 9:38 am

    Personally, I think we should decimalise time and just go by Unix timestamps. People would be able work whatever kiloseconds they choose, and there’s no such thing as a rush myriasecond anymore.

    Maybe _this_ is why the Mayan calendar ends in 2012 – they realised it would become obsolete this year!

    • March 11, 2012 at 10:41 am

      After researching my piece on Leap Year for the NY Times Learning network, I kind of got into the Hanke-Henry permanent calendar. I think it does away with DST in addition to preserving days-of-week from year to year.

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