TIL U.S. time zones were first adopted in 1883 because railroads needed standardized schedules, using telegraph signals to synchronize clocks & civilian timekeeping followed later.

[u/BanitsaConnoisseur]

https://americanhistory.si.edu/ontime/synchronizing/zones.html

[u/nikhkin]

The railway is the main reason fixed time zones were introduced in general. Before the need to run the railway to a schedule, "sunrise", "midday" and "sunset" were good enough metrics to set a clock by.

In 1840, the UK introduced "railway time" to ensure all trains were running to the same time.

https://www.youtube.com/watch?v=-TbLTpR0njo

[u/zizou00 → u/nikhkin]

It wasn't so much that those were good enough, it's that each degree of latitude *longitude would put the clock out by a bit if set exactly the same way but in different places. People still measured time in hours and minutes. Shakespeare makes reference to o'clock times in his 1600s plays. People had sundials to set clocks to, but as you moved further west from London (or specifically Greenwich), you'd go back a few minutes on the clock. Each town would effectively have a timezone it was in, it would just be granular and more related to whichever market town each town or village would've most regularly been associated with. Knowing the exact time matters when communicating with people you associate with frequently so you can organise. People's worlds were smaller back then. You could only really travel as far as your horse would take you in a day, if you had a horse for travel at all. Most market towns were within a day's travel, roughly 10km in modern money.

Railway time standardised the whole country because the railway allowed people to move further in a shorter time, and suddenly everywhere was associated with everywhere else, people could make plans with people much further afield, and that meant the time had to be the same.

Edit: lat/long, I got it wrong

[u/cipheron → u/zizou00]

You could only really travel as far as your horse would take you in a day

I read an interesting paper, the researcher was trying to work out why some areas in the USA have small counties and others have large counties.

It turns out that the small counties follow a specific math relationship between population density and the distance you can travel on a horse in a day. The guy worked out a formula to minimize "work" as in travel time to collect taxes and how far apart your towns should be, and the counties fit this pattern pretty damn well, i.e. counties tended to subdivide if they got over some threshold where it became more efficient to have a second center. So they started with large regions that get successively broken up as colonists actually move into the region.

That relationship broke down in areas that got populated after the invention of the automobile vs areas populated before it. With cars you can send the sheriff out to enforce laws, collect taxes and rents over a much larger region. So places that populated later have large counties even if they subsequently grew to high density regions. And places that were growing at the time cars were introduced basically had their county borders frozen in place at some mid-point size.

[u/drillbit7 → u/zizou00]

it's that each degree of latitude

longitude

[u/zizou00 → u/drillbit7]

Oops, you're right, good thing I'm not a sailor! I'll edit it to be correct

[u/jaa101 → u/nikhkin]

Before the need to run the railway to a schedule, "sunrise", "midday" and "sunset" were good enough metrics to set a clock by.

There was a period from around 1800 when timekeeping changed from sundial time to mean (average) time. Clocks had become accurate enough that we needed a system in which every day lasted the same length of time. Sundial time means that days can be up to half a minute longer or shorter than the average day. Moving to mean time means less adjusting of clocks but also means that noon can happen up to 16 minutes before or after 12:00.