4 ms·

It worked exactly the way you've described until the advent of the industrial revolution and the trains. That's when all of England moved to single time, and ot

by maratc 5y ago

It worked exactly the way you've described until the advent of the industrial revolution and the trains. That's when all of England moved to single time, and other countries soon followed. Assuming you're past sixth grade, please answer the following question: the train leaves point A at noon sharp, and takes 3 hours to reach point B. What time will the train arrive at point B?

chrismorgan 5y ago
Answer: you just have a bigger time zone table, like https://www.netburner.com/wp-content/uploads/2020/02/Comparative-time-table.jpg https://www.netburner.com/wp-content/uploads/2020/02/Compara..., where you can see that A (which perhaps stands for Albany, N.Y.) is 14 minutes ahead of Washington D.C., and B (which is perhaps Baltimore, Md.) is 2 minutes ahead, so this rather fast train will arrive at 2:48pm (12:00 noon + 3 hours − 14 minutes + 2 minutes). It’s really no different from the coarse-grained time zone system, just more complicated because you have much bigger tables. (I’m pretty sure I’ve seen a picture of a railway’s time zone table from before the 1883 change to coarser time zones, sorted by station, with most deltas being one or two minutes, but I can’t find it now.)
- maratc 5y ago
  This also depends on the day, since "noon to noon" is no longer 24 hours 0 minutes 0 seconds. So these tables aren't just "much bigger", they are also changing daily. We would have to either 1. redefine what a "day" is, or 2. redefine what a "second" is — and that's on a daily basis. Suggesting the whole population starts doing these calculations every time they need to figure out things like "can I take the noon train and still be there on time for my meeting at 3:15 pm" or "my boss asked me to call him at 9am his time, what local time should I place the call?" is completely pointless.
  - chrismorgan 5y ago
    I was assuming we were reverting to how things were two hundred years ago (when a day was of 24 hours of fixed duration and noon was correlated with solar noon, though the precise function I know not), not two thousand (when solar day and solar night were divided into 12 variable hours). If you were really aiming to have noon be solar noon each day… yeah, much misery would ensue.
    - maratc 5y ago
      I wasn't aiming for anything but GP seemingly was: > We should redefine noon to the time when the local sun is most directly overhead. The local sun is "most directly overhead" at a different time each day at any place (maybe with the exception of Arctic circles when it's not up at all).
    - bluGill 5y ago
      No, it is useful to have a synchronized clock for some activities.
bluGill 5y ago
No we didn't. Before timezones every town had their own clock and they were not synchronized in anyway. I'm saying one timezone for the world. For me noon becomes 6:43 pm (or something like that)
- dhimes 5y ago
  They were synchronized to the Sun- local apparent noon.
  - bluGill 5y ago
    Only sort of. In general each town had their own time keeper, and clock. Some would adjust their clocks to sun noon more often than others, and some were stricter about doing it. So you could never be sure that the next town west had noon later than this town (though in practice mechanical clocks were so bad that you couldn't measure it) Also in some area time was set by sunset not local noon. (Jewish cares about when the sunsets - I suspect others as well)
    - maratc 5y ago
      > Jewish cares about when the sunsets It's only for days of the week. The time is still the local time. Since it's very important in Judaism to not do any work on Shabbat (the Jewish day of rest), there are two distinct Shabbat's in Israel. One is "religious" Shabbat (translated to English as "Shabbat") which starts at sunset on Friday and ends after sunset on Saturday, lasting about 25 hours. The other is "civic" Shabbat (translated to English as "Saturday"), which starts (as everywhere) after 23:59 Friday and ends at 00:00 when Sunday comes. So when you invite a friend over on "Shabbat evening" there's an ambiguity: it's unclear whether that relates to Friday evening (the evening of "Shabbat") or Saturday evening (the evening of, ahem, "Saturday"). To resolve that ambiguity, modern Hebrew has a distinct term for "the evening after Shabbat that comes on Saturday evening".
- maratc 5y ago
  > For me noon becomes 6:43 pm (or something like that) Interesting. At my place, the 23rd of September started at 00:00 and will end at 23:59. When did that date start at your place? Also, that Sunday (September 26th) when I'm supposed to get my day off work — is that the day where it's Saturday a.m. and Sunday p.m, or is it the day when it's Sunday a.m. and Monday p.m.? I'm confused.

by maratc 5y ago

chrismorgan 5y ago

Answer: you just have a bigger time zone table, like https://www.netburner.com/wp-content/uploads/2020/02/Comparative-time-table.jpg https://www.netburner.com/wp-content/uploads/2020/02/Compara..., where you can see that A (which perhaps stands for Albany, N.Y.) is 14 minutes ahead of Washington D.C., and B (which is perhaps Baltimore, Md.) is 2 minutes ahead, so this rather fast train will arrive at 2:48pm (12:00 noon + 3 hours − 14 minutes + 2 minutes). It’s really no different from the coarse-grained time zone system, just more complicated because you have much bigger tables. (I’m pretty sure I’ve seen a picture of a railway’s time zone table from before the 1883 change to coarser time zones, sorted by station, with most deltas being one or two minutes, but I can’t find it now.)

maratc 5y ago
This also depends on the day, since "noon to noon" is no longer 24 hours 0 minutes 0 seconds. So these tables aren't just "much bigger", they are also changing daily. We would have to either 1. redefine what a "day" is, or 2. redefine what a "second" is — and that's on a daily basis. Suggesting the whole population starts doing these calculations every time they need to figure out things like "can I take the noon train and still be there on time for my meeting at 3:15 pm" or "my boss asked me to call him at 9am his time, what local time should I place the call?" is completely pointless.
- chrismorgan 5y ago
  I was assuming we were reverting to how things were two hundred years ago (when a day was of 24 hours of fixed duration and noon was correlated with solar noon, though the precise function I know not), not two thousand (when solar day and solar night were divided into 12 variable hours). If you were really aiming to have noon be solar noon each day… yeah, much misery would ensue.
  - maratc 5y ago
    I wasn't aiming for anything but GP seemingly was: > We should redefine noon to the time when the local sun is most directly overhead. The local sun is "most directly overhead" at a different time each day at any place (maybe with the exception of Arctic circles when it's not up at all).
  - bluGill 5y ago
    No, it is useful to have a synchronized clock for some activities.

bluGill 5y ago

No we didn't. Before timezones every town had their own clock and they were not synchronized in anyway. I'm saying one timezone for the world. For me noon becomes 6:43 pm (or something like that)

dhimes 5y ago
They were synchronized to the Sun- local apparent noon.
- bluGill 5y ago
  Only sort of. In general each town had their own time keeper, and clock. Some would adjust their clocks to sun noon more often than others, and some were stricter about doing it. So you could never be sure that the next town west had noon later than this town (though in practice mechanical clocks were so bad that you couldn't measure it) Also in some area time was set by sunset not local noon. (Jewish cares about when the sunsets - I suspect others as well)
  - maratc 5y ago
    > Jewish cares about when the sunsets It's only for days of the week. The time is still the local time. Since it's very important in Judaism to not do any work on Shabbat (the Jewish day of rest), there are two distinct Shabbat's in Israel. One is "religious" Shabbat (translated to English as "Shabbat") which starts at sunset on Friday and ends after sunset on Saturday, lasting about 25 hours. The other is "civic" Shabbat (translated to English as "Saturday"), which starts (as everywhere) after 23:59 Friday and ends at 00:00 when Sunday comes. So when you invite a friend over on "Shabbat evening" there's an ambiguity: it's unclear whether that relates to Friday evening (the evening of "Shabbat") or Saturday evening (the evening of, ahem, "Saturday"). To resolve that ambiguity, modern Hebrew has a distinct term for "the evening after Shabbat that comes on Saturday evening".
maratc 5y ago
> For me noon becomes 6:43 pm (or something like that) Interesting. At my place, the 23rd of September started at 00:00 and will end at 23:59. When did that date start at your place? Also, that Sunday (September 26th) when I'm supposed to get my day off work — is that the day where it's Saturday a.m. and Sunday p.m, or is it the day when it's Sunday a.m. and Monday p.m.? I'm confused.