TIL: Sweden had February 30 in 1712 https://en.wikipedia.org/wiki/1712_in_Sweden , so I decided to see how chrono handled that.

use chrono::TimeZone;
use chrono_tz::Europe::Stockholm;

fn main() {
    let feb30 =  Stockholm.ymd(1712,2,30);
    println!("Date: {:?}", feb30);
}

 target/debug/feb30
thread 'main' panicked at /home/snaggen/.cargo/registry/src/index.crates.io-6f17d22bba15001f/chrono-0.4.34/src/offset/mod.rs:252:40:
No such local time
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Result (as expected): Not well! 😄

I also tested Java with

ZonedDateTime feb30 = ZonedDateTime.of(1712,2,30, 0,0,0,0, ZoneId.of("Europe/Stockholm"));

with simmilar result

java.time.DateTimeException: Invalid date 'FEBRUARY 30'

So, lets take a minute of silence for all the programmers of history related software, may the spagetti monster have mercy on their souls.

    • sugar_in_your_tea@sh.itjust.works
      8·
      1 year ago

      Even just sticking with UNIX timestamps and relying on a library, dealing with time zones still sucks. Inevitably, your backend and frontend libraries will have some difference in some case that matters for some customer. And it won’t happen just after release, but some months down the road when one country somewhere changes their laws and your libraries don’t get updated in time, or maybe there’s a bug like in the OP.

      Madness lies everywhere when talking about time.

      We should all do ourselves a favor and follow UTC time everywhere. There’s still leap seconds and leap days to deal with, but so many problems just disappear if everyone uses the same time. The sun may come up at 20:00 and go down at 09:00, but your stores can just adjust their hours and it’s totally fine. You won’t ever have to worry about missing a meeting because the organizer’s software and yours got out of sync, and you’ll never have to mentally convert times on a call.

      It’s a small price to pay, but for all our sanity, just use UTC time.

      • robinm@programming.dev
        4·
        1 year ago

        The issue is that the notion of “tomorrow” becomes quite hard to express. If it’s 20:00 when the sun rose, when does tomorrow starts? In 5 hours ?

        • sugar_in_your_tea@sh.itjust.works
          1·
          1 year ago

          No, I think that would still be based on local sun time, and we’d just not use it much when talking to people outside that time zone. So in a video call, we’d just say, “let’s meet at 08:00”, which could be “tomorrow” for some listeners, and could be later today for others. A day would still be from sun-up to sun-down, in colloquial terms, but dates would be from 00:00 to 23:59, so if you wanted to be precise, you’d just say the date.