Steve, thank you for linking the WikiMedia Commons SVG, I like vector graphics, particularly ones that are also infographics. However, it does not display what is really going on with DST. Although everybody has stories about how it came about and was implemented and why (for factories, for gas lamps, whatever) including the urban legend that Ben Franklin invented it, the general goal behind all of those specific purposes is to align more closely the clock day with the light day. For example, a clock says 0600; how light is it outside? Is it dawn? Earlier? Later? Well, that changes throughout the year because the Earth is tilted. It would not if the Earth was vertical (to clarify, if it's pole of rotation was parallel to the pole of orbit) and a year was exactly 365 days, and each day were exactly 24 hours, and if [a more minor factor] there were no precession, and so on). So what DST is really doing is shifting the time scale 'down' relative to the light scale (in the WM diagram [or perhaps *dia*gram]) to more closely 'fit' that sunset/sunrise curve. Now, yes, we might be able to simply ignore that curve, pick a place for the time day to start and stick with it; after all, electric lights are ubiquitous and few of our jobs actually depend on being up at the same time as the sun (perhaps farmers still, but there are fewer and fewer of them). But I am saying I think it is possible and doable to have a system that follows the variance in the amount of daylight versus dark throughout the year, if we as a society think it is valuable to go that route. After all, before the invention of more and more specialised calendar systems that is what people would have considered a day: from sunrise to sunset and the following dark period, no matter what time of year. -Arlo James Barnes
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