1883: U.S. and Canadian railways adopt five standardized time zones to replace the multiplicity of local times in communities across the continent. Everyone would soon be operating on "railroad time."

Noon on a well-made, properly paced sundial is whenever the sun is highest right there. The advent of mechanical timekeeping in the Middle Ages didn't change that. Noon in your town was whenever the sun was highest right there. If that meant that noon in a town a hundred miles away might be a few minutes ahead or behind your local noon, big deal. You couldn't get there fast enough for it to matter.

The railroad changed that, starting in the early 19th century. The horse had been the fastest way to move people and goods from one place to another since the species was domesticated, as early as 4000 B.C. The six-millennium reign ended quickly as networks of rails spread across North America and Europe at mid-century.

But timekeeping was still medieval. Local jewelers synchronized their customers' watches to local solar noon. In a small town with one jeweler, everyone might use the same time settings. In a large city, the many jewelers' various observations might diverge by several minutes. Some places achieved citywide synchronization by dropping a time ball on a highly visible tower at noon every day. (It worked better than ringing a bell. You might hear a great bell two or three miles away, but that would be 10 or 15 seconds after it was struck.)

Thousands of municipalities each worked to their local times. The Chicago Tribune, for instance, showed 27 local times in Michigan, 38 in Wisconsin, 27 in Illinois and 23 in Indiana.

Railroad timetables used about a hundred different standards. A single railroad that traveled east to west would use multiple noons: The Union Pacific, for example, had six different settings in what are today the Central and Mountain zones. The Union Station that served multiple railroads in a big city might have five or six different clocks, one for each railroad in the station, each running on is own time.

As new technology let railroad trains go even faster, the need for a better system was increasingly evident. The multiplicity of local time settings also created complexity and confusion for operators and users of the telegraph (whose lines usually followed the rails) and the newfangled telephone.

England, Scotland and Wales standardized to Greenwich Mean Time on Dec. 6, 1848, after two decades of urging by Sir John Herschel. In the United States, Charles F.Dowd, principal of Temple Grove Ladies' Seminary at Saratoga Springs, New York, pushed the case in 1869 for four time zones, each the width of 15 degrees of longitude. Professor Benjamin Pierce of Harvard picked up the cudgels in the 1870s.

The cause was also championed by William F. Allen, secretary of the General Time Convention, the group the railways had formed to coordinate their schedules. (That group evolved into Association of American Railroads.)

The railroads finally agreed to General Time Convention on Oct. 11, 1883. They adopted five time zones: Intercolonial Time (now known as Atlantic Time in eastern Canada) and the Eastern, Central, Mountain and Pacific time zones. The U.S. zones were based on solar noon at 75, 90, 105 and 120 degrees west of Greenwich.

When the new system took effect at noon on Nov. 18, conductors all over the United States and Canada resynchronized their watches from their individual railroads' times to the new standard times. Some folks objected, thinking they were being robbed of minutes, just as people felt robbed of days when the calendar shifted from Julian to Gregorian in previous centuries.

But businesses followed the lead of the railroads, and people showed up for work when employers said they needed to, and customers visited stores when shopkeepers said they were open. And people arrived at the railroad station to catch trains that ran on the same time settings as the watches in their pockets and the clocks on the sidewalks.

So convenient was the system of time zones that it thrived entirely on the say-so of the railroads for 35 years. Congress did not enact Standard Time until March 19, 1918, when it also initiated Daylight Saving Time as an efficiency measure during World War I.

Source: FREMO (Friendship Association of European Model Railroaders)

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Home test kits used to be for things like finding out if you're pregnant or checking the hot tub's chlorine level. Now over-the-counter chemical tests can tell you if your spouse is cheating or if your new home ever doubled as a meth lab. Yes, science now makes house calls.

The Kit (left) Tests for STDs Some ailments are too embarrassing for the family doc. This kit, part of the CDC's Infertility Prevention Project, lets you swab your privates in private. Send in the sample and a lab runs free tests for chlamydia, gonorrhea, and trichomoniasis.

CheckMate Tests for Infidelity Riskay may rap about smelling her man's member to sniff out a cheater. You may prefer to use CheckMate. Rub the blotting paper in the suspect's underpants, then dip it in the included chemicals — if the pad turns purple, they've got some explaining to do.

Lead Test Kit Tests for Lead You never know what shortcuts were taken to make your tyke's Hannah Montana doll. Unless, of course, you swab the toy with indicator solution. If the solution on the swab or on the toy turns yellow, brown, or black, you've got lead.

MethChek 50 Tests for Meth Residue Foreclosures are a great chance to score a house on the cheap. But how do you know that three-bedroom ranch wasn't once a suburban meth lab? By swabbing the walls with this immunoassay kit, of course!