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| Fall back, Spring forward |
In an effort to find some meaning behind the madness, I looked up some little-known (to me, at least) DST facts.
- DST is generally not observed near the equator, where sunrise times do not vary enough to justify it. For example, southern Brazil observes it while equatorial Brazil does not; Asia and Africa generally do not observe it.
- Although they did not fix their schedules to the clock in the modern sense, ancient civilizations adjusted daily schedules to the sun more flexibly than DST does, often dividing daylight into twelve hours regardless of daytime so that each daylight hour became progressively longer during spring and shorter during autumn.
- Port Arthur, Ontario, Canada, was the first city in the world to enact DST on July 1, 1908; the United States adopted daylight saving in 1918.
- Daylight saving has caused controversy since it began. Historically, retailing, sports, and tourism interests have favored daylight saving, while agricultural and evening entertainment interests have opposed it. Its initial adoption was prompted by energy crises and war.
- Clock shifts are usually scheduled at, or soon after, midnight and on a weekend to lessen disruption to weekday schedules. A one-hour shift is customary but twenty minute and two hour shifts have been used in the past.
- In all countries that use daylight saving, the clock is advanced in spring and set back in autumn; the spring change reduces the length of that day and the autumn change increases it.
- From year to year, the shift dates may change for political and social reasons.
- DST is commonly not observed during most of winter, because the days are shorter then.
- Since DST is applied to various communities, its effects may be very different depending on their culture, light levels, geography, and climate. Because of this variation, the costs and benefits may differ from place to place. Some areas may adopt DST simply as a matter of coordination with others rather than for any direct benefits.
- A 2017 study in the American Economic Journal: Applied Economics estimated that "the transition into DST caused over 30 deaths at a social cost of $275 million annually," primarily by increasing sleep deprivation. Transitions into and out of DST were also found to increase the risk of heart attack by 10 percent.
- DST's clock shifts have the obvious disadvantage of complexity. People must remember to change their clocks; this can be time-consuming, particularly for mechanical clocks that cannot be moved backward safely. People who work across time zone boundaries need to keep track of multiple DST rules, as not all locations observe DST or observe it the same way. Disruption to meetings, travel, broadcasts, billing systems, and records management is common, and can be expensive.
- When the DST rules change, software developers must test and perhaps modify many programs, and users must install updates and restart applications. Consumers must update devices such as programmable thermostats with the correct DST rules or manually adjust the devices' clocks. A common strategy to resolve these problems in computer systems is to express time using the Coordinated Universal Time (UTC) rather than the local time zone.
* Has anyone else been saying it "Daylight Savings Time" or is it just me? It feels awkward leaving the "s" off. As it turns out, there's a Wikipedia entry on that. According to the Oxford Dictionary of American Usage and Style: "Although the singular form 'daylight saving time' is the original one, dating from the early 20th century--and is preferred by some usage critics--the plural form is now extremely common in American English."
