With today being the day that we return to standard time, this week has seen the semi-annual discussion about abolishing the switches between daylight savings and standard time.  It says something about where we are as a county that most of the discussions begin with the assumption that daylight savings is the norm and standard time is the aberration.

So let’s start with a brief history of how we track time.  For most of history, there was little need to keep track of time or at least not to keep an exact track of time.  Key celestial events (the equinoxes, the solstices, new moons, full moons) were the central feature of the calendar often marked by religious festivities.  But on a day-to-day basis, what mattered was sunrise and sunset.  Since most people lived on the property of their boss (whether semi-voluntarily as hired servants or apprentices or involuntarily as serfs, peasants, or slaves), the day started when the supervisor said it did (typically shortly after sunrise) and ended when the supervisor said it did (around sunset).  Other than sunrise or sunset, the only other key time marker was noon — when the sun was directly overhead.  If people needed to mark time, they used sundials (most accurate on the equinox or if you were close to the equator) or hourglasses.

Over time, mechanical clocks and watches replaced hour glasses as a way to keep track of time.  And, as workers stopped living on their employers’ property,  the town clocks became the official local time.  In most areas, noon remained when the sun was directly overhead.

But things changed again as the economy changed.  The development of trains led to a need to have some means of measuring time that applied over the entirety of a train’s route.  The consequence of the earth’s rotation is that as you move east or west, the time when the sun is directly overhead changes.  One degree of longitude represents approximately four minutes of time.  And one degree of longitude is typically one or two counties over in the U.S.  For a train, you do not want your conductors to  have to reset their watches at every stop to match the local clocks.  But you want your conductors to leave exactly at the scheduled times, and you want your customers to know when — in local time — the train is scheduled to depart.  Hence, the development in the nineteenth century of standard time and time zones.  Each time zone represents approximately fifteen degrees of longitude (or one hour of time).  Eventually, by the end of the nineteenth century, the government had adopted standard time as the uniform time.  Because the boundaries are rough and cover approximately sixty minutes worth of difference, standard time is not quite the same as sun time.  Simply put, sun time in the western part of the time zone is approximately thirty minutes after the official time (i.e. the sun is directly overhead at around 12:30 rather than noon) and sun time in the eastern part of the time zone is approximately thirty minutes before the official time (i.e. the sun is directly overhead at around 11:30 rather than noon).

In the early twentieth century,  the idea arose to shift the clocks forward during the summer (such that the sun was directly overhead at 1 p.m. rather than noon).  This had the effect of shifting an hour of sunshine from the morning to the evening.  There is a lot of debate about why this occurred — some attribute the change to farm interests (wanting more time in the evening to work in the field) and others attribute the change to business interests (wanting more time after work for people to shop).

While noon is relatively constant, sunrise and sunset is not.  At the equinox, sunrise is at approximately 6 a.m. local time and sunset is at approximately 6 p.m. local time.  But as the length of the day gets longer in summer and shorter in winter, the time of sunset and sunrise changes.  How much the time of sunrise and sunset changes depends on how far north you are.  In the central U.S., the change is between one and two minutes per day.  The body is somewhat used to these gradual changes and easily adjusts.  But bigger changes are harder to adjust too.  This phenomena is most noted by “jet lag” after a shift of multiple time zones when the amount of daylight tells the body that it should be awake but the exhaustion of being up for twenty hours already tells the body that it should be asleep.  But even a one hour shift has some biological and psychological impacts on the body.

And the change in daylight savings vs. standard is, in some ways, more impactful than a time zone change.  With jet lag, our body eventually catches up with the sun, but the body is still trying to wake up at the correct local time.  With the switch between daylight savings and standard time, we are retraining our body as to the right local time to wake up and go to sleep.  Thus, there is a benefit to opting for either daylight time or standard time as the right way to measure time.

For some of us, particularly those who are light sensitive, there is a benefit to having the switch.  Daylight savings time means that sunrise does not get too early in the day  With daylight savings time, in the central U.S. sunrise is only around 6 a.m. even at the time of the summer solstice.   And by switching back  to standard time for the winter, sunrise does not get much later than 7 a.m.  (Of course, moving the switch closer to the equinox would balance things out better.)

There are good arguments for using standard time or daylight savings time throughout the year or (if we are going to split the year) for when we should make the switch.  The fact that the way that we have structured our economy creates a benefit to not using the traditional sun time says something.  And the fact that we think that daylight savings time is traditional sun time says something about people’s understanding of reality.  Both of these issues are at least as worthy of debate as what we should do about daylight’s savings time.

It is also worthy of note that this debate is one of those issues that pits the states against the national government.  Time zones and daylight savings time is governed by federal law.  While about half of the states have passed laws and resolutions calling for a change, it will take federal action to “resolve” this issue (at least until the next time that people agitate for a change).  And for the very reasons that we have time zones, the decision ultimately should be made at the federal level.  State boundaries are only slightly better than city boundaries for requiring people to adjust their clocks.  While there have to be lines where time zones change, fewer time zone changes are better than more time zone changes.  Even better would be for time zones to be set internationally.  The U.S. is large enough that national control over time zones is not a problem here, but — in other parts of the world — it would be problematic if each tiny nation set its own time.