Have an optional parameter that outputs the timezone in `.toISO8601()`

[Hari-07]

This tracker is for issues related to:dart:core

• Dart version and tooling diagnostic info (dart info)

Dart info

#### General info - Dart 3.7.0-140.0.dev (dev) (Wed Nov 13 00:06:32 2024 -0800) on "macos_arm64" - on macos / Version 15.1 (Build 24B83) - locale is en-IN

Process info

Memory	CPU	Elapsed time	Command line
23 MB	0.0%	14:08	dart devtools --machine --allow-embedding --dtd-uri ws:/oUaguuA3EYlbM0y0
12 MB	0.0%	05:00:52	dart language-server --protocol=lsp
47 MB	0.0%	21:04	dart language-server --protocol=lsp --client-id=VS-Code --client-version=3.100.0
86 MB	0.0%	14:08	dart language-server --protocol=lsp --client-id=VS-Code --client-version=3.100.0
2 MB	0.0%	02-07:33:07	dart pub get --no-example
23 MB	0.0%	21:04	dart tooling-daemon --machine
26 MB	0.0%	14:08	dart tooling-daemon --machine
51 MB	0.0%	14:08	flutter_tools.snapshot daemon

PR: https://dart-review.googlesource.com/c/sdk/+/395760

[dart-github-bot]

Summary: The user requests an optional parameter for the .toUTC8601() method to include timezone information in the output. The issue lacks specifics on which library this method belongs to (it's not standard in dart:core).

Thank you for your report! To help us understand and address your request, could you please clarify the following:

• Which library contains the .toUTC8601() method? (e.g., a third-party package, a custom library) Please provide the package name and version if it's a package.
• Could you provide a minimal, reproducible code example demonstrating the issue? This will help us understand the context and behavior you're observing.
• What is your desired behavior? A concrete example of the expected output with the timezone included would be very helpful.
• What is the current behavior? What output are you getting now?

Providing this information will greatly assist us in investigating and resolving your issue.

[Hari-07]

• Library is dart:core

[Hari-07]

Minimal example:

void main() async {
  final now = DateTime.now();
  print(now.toIso8601String());
}

There's no option to print with timezone. For eg: 2024-11-17T22:52:28.292+05:30

[lrhn]

The information is available, so it's clearly possible to include it in the toIso8601String.

The information cannot be read back to an equivalent DateTime.
The original DateTime is local-time, and the DateTime created by parsing a string with an explicit time zone offset will be an UTC DateTime, which discards the time zone offset for a UTC time of the same point in time.

It means that for round-tripping this is equivalent to just doing .toUtc() first.
So round-tripping shouldn't be the goal here. Target it is to have a textual representation of the actual local time, even if it might not be possible to recreate it again as a local DateTime in any other time zone.

It does make sense then.

[lrhn]

The easy alternative is to use package:timezone and its TZDateTime class instead, which outputs the time-zone offset in its toIso8601String method.

[Hari-07]

Sure, if you wanna go down that route its super easy to just have an extension method that always has the timezone rather than including a package just for this. I believe timezone also requires using a different type than DateTime which can be a whole thing

My motivation for getting it into dart itself is that the Iso8601 spec includes the timezone (optionally)

A potential usecase (I havent come across this myself yet so not sure if there's existing workarounds) but most serializing packages including json_serializable uses toIso8601String . So if a client side timestamp is sent up to the server, this would enable the timezone information to be present