By the Numbers, DST is the Simplest Approximation of Natural Time [Hub Debate]

Top GraphOur bodies internal clock synchronizes with sunrise; Daylight Savings Time averages out mechanical 24 hour clock time with the seasonal sunrise shift.

Our time zones and common time are a political decision based on how we want to run our society, not some mandate of nature. Changing our common time from Mountain Daylight Time causes confusion.
What is time?

This is not a philosophical discussion, but a good place to start as we consider changing the way Utah keeps time. Prior to computers, watches and railroads, time came from the sun. Humans, like most animals, are adapted to use day light for taking care of our physical needs; our bodies start to produce melatonin and wind down as day light fades to night. Historically man has counted hours since dawn and found that precision adequate to our needs.
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Historical Wall Sundial, Dutch East India Company Fort, Cape Town (credit: Scott James)
The modern world relies upon high precision 24 hour clocks, enabling synchronization of technology and great economic benefits. We’ve defined time zones along political boundaries based on the average local noon in fixed time zone areas like the Rockies, continental Europe and China. We expect businesses to keep posted hours and employers expect us to show up at the same nominal clock time every morning. But our bodies internal clocks are chemically based on daylight, and our bodies know the clock’s time is not the same as nature’s.
Pretending that clocks are a natural state of timekeeping as others in this debate have suggested is absurd. Our children follow the natural, historical time keeping method that starts at dawn. Through a simple, universally understood, twice annual, 1 hour clock shift, DST pushes our nominal clock time closer to natural dawn time during summer months. The summer sun has been waking me up naturally around 6:30 DST for the last couple months. As detailed below, DST constrains daily Utah nominal dawn times in a 2 hour window, rather than 3 hours of variation. The circadian rhythm that DST naysayers frequently cite is mostly controlled by ambient light, to the point that night shift workers and people who sleep in high light levels have ~50% higher breast cancer rates.
Unlike the cancer risks from night time light exposure, DST grogginess from the time change can be completely alleviated by simply moving your alarm forward or back 10 minutes a day/week before the time change.
If you’re still convinced unchanging, politically averaged, mechanical clock time is best for Utah, the simplest, and most logical way for Utah to abandon DST is to join our southern neighbor, Arizona. But, Arizona’s latitude makes Daylight Savings less valuable. At our respective population centers, Phoenix summer sun rise and set times go from 5:19 to 19:4114:22 hours of daylight. Salt Lake MST sun rise and set times go from 4:56 to 20:0215:06 hours of daylight. Abandoning DST means your kids will be getting up at 5 AM since our summer sun rises 23 minutes earlier than Phoenix.

Summer Rise Set Hours of light
Phoenix 05:19 19:41 14:22
MDT SLC 05:56 21:02 15:06
MST SLC 04:56 20:02
earlier dawn 00:23 longer day 00:44
Winter Rise Set Hours of light
Phoenix 07:28 17:25 09:57
SLC 07:48 17:03 09:15
later dawn 00:20 shorter day 00:42
SLC MST annual dawn window
07:48 04:56 02:52

Some have suggested we could remove the annoyance of semiannual clock changes by permanently moving to year round +1 hour DST. But come winter, this would likely increase accidents from dark commutes on icy roads with sun rise near 9 AM. This is compounded by the fact that the coldest temperatures usually come right before dawn. Phoenix rarely needs to clear roads; their 7:28 -17:25 winter day yields 10 hours of light, while Salt Lake’s 7:48-17:03 cuts us down to 9:15 hours. Much of the Wasatch front has an even later sunrise as our tall mountains push our horizon higher, making icy roads more treacherous later into the morning.

Now that we’ve discussed several facts about how we measure and perceive time, we’re left with a political decision about how we want to define our common time. State services and economic activity, especially snow removal, benefit from more morning light in the winter, while the economy benefits from standardized business hours that take advantage of seasonal change. Any change to DST should be taken in consideration of our neighboring states– CO, ID, WY– to minimize time confusion and resulting economic losses. Abandoning the rest of America on DST and joining Arizona has more costs and less benefit for Utah than Arizona. Like many harmless, existing political boundaries and decisions, Utah’s current use of DST is best left unchanged.

DST helps align our digital clock reality with natural, seasonal light fluctuations and is the simplest solution that accounts for Utah’s economic needs.

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