ZoneRulesException without timezone

[marcadella]

The following code works in scala: LocalDateTime.now().
But in Scalajs it throws: java.time.zone.ZoneRulesException: Unknown time-zone ID: Europe/Oslo.
I do not intend to use any timezone.
Scalajs version: 1.5.0
scala-java-time version: 2.1.0

[marcadella]

I guess it is because, contrary to what the doc says, the default system timezone is used by default instead of UTC. If it is not what the doc mean, then it should be fixed to specify that one need to use UTC explicitly. Ex: LocalDateTime.now(ZoneId.of("UTC)) works in ScalaJs.

[cquiroz]

I think you're right. it will try to guess the local timezone, it is better to set a default one.
PRs to the documentation are welcome

[OndrejSpanel]

I came to this issue because I started to get this exception after upgrading from udash-0.8.0 to udash-0.9.0.

Udash used https://github.com/zoepepper/scalajs-jsjoda in previous versions. I am not sure what its implementation of LocalDateTime.now was, but it did not throw any exceptions. Most likely it just calls ZoneId.systemDefault() from JS Joda.

[OndrejSpanel]

it is better to set a default one.

When I am using this in a frontend (browser), what way can I use to set the default timezone to something reasonable? I do not want users to have to tell me their timezone, there surely must by some simpler way.

[cquiroz]

The code tries to guess the timezone but it is not always successful
https://github.com/cquiroz/scala-java-time/blob/master/core/js/src/main/scala/java/util/TimeZone.scala#L28

I'd suggest you try to verify what is being selected with that piece of code.

[2072]

I get the same issue with v2.6.0: ZoneRulesException: Unknown time-zone ID: Europe/Paris just by calling ZoneId.systemDefault() which in my case returns Europe/Paris which is correct and works on the JVM side.

If I put my workstation in UTC it works.

(I'm using Scala 3.7.1 and ScalaJS 1.19.0)

Edit: OK just read the doc and it turns out that one needs an additional library for ZoneId.systemDefault() to not crash. It might be useful to say so in the exception message like ("IANA Time Zone Database not available, RTFM"), it's the information @OndrejSpanel needed.

[cquiroz]

the need for a tzdb is stated on the documentation pages

https://cquiroz.github.io/scala-java-time/

[2072]

Of course it is but as you know no one ever reads the documentation.... I myself lost more than 1 hour on this issue, if it happened to me it means it has and will happen to many other people too.

If you don't want to improve the error message when the IANA db is missing, another improvement could be to just add the second library to the README.md with a comment telling that it can be removed if you are sure your code is not using time zones. (at least if someone removes it and see the unknown time-zone id message they will know what to do).

In fact there is an error in the readme.md: it states

To get started with SBT, add one (or both) of these dependencies:

libraryDependencies += "io.github.cquiroz" %%% "scala-java-time" % "2.5.0"

but there is only one dependency... I've made a pull request to fix the readme.

[cquiroz]

yes, thanks a lot for the readme PR