Does NodaTime support AYN (per ISO 8601)?

[Roke Beedell (RokeJulianLockhart)]

As I originally asked more verbosely at github.com/dotnet/runtime/discussions/109687 (please read it), does NodaTime support ISO 8601-1:2019+A1:2022's astronomical year numbering?

I ask because I want to be able to utilize it to parse negative years in dates. To my knowledge, ca-iso8601 backdates the Gregorian calendar for this purpose.

This is my first time participating in Google Groups, so please understand if I utilize it incorrectly. Being <30, mailing lists are somewhat foreign to me.

[Jon Skeet]

I'll need to double check, but I'm pretty sure we support negative "absolute" years out of the box, e.g. -0002-06-19T00:00:00 meaning "June 19th, 3 BCE (proleptic Gregorian)". But I don't think we support a leading + at the moment.

Please file an issue on GitHub for that l, with as many details as I may have missed.

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[Jon Skeet]

Right, I've just confirmed what I thought: we don't support "+", but parsing both "-0002-06-19" and "0002-06-19" work as expected. For the moment, if you need "+" support, I'd suggest adding a small amount of code to your application code to remove a leading "+" when parsing and add one when formatting - it's ugly, but hopefully just about good enough until Noda Time supports the "+" fully.

Note that the range of years supported by Noda Time is 9999 BCE (-9998 AN) to 9999 CE (+9999 AN).

Jon

using NodaTime.Text;

Test("-0002-06-19");
Test("0002-06-19");
// Fails
Test("+0002-06-19");

void Test(string text)
{
    var pattern = LocalDatePattern.Iso;
    var date = pattern.Parse(text).Value;
    Console.WriteLine($"{text} => {date} => {pattern.Format(date)}");
}

[Roke Beedell (RokeJulianLockhart)]

Thank you, Jon. Lots. I've filed https://github.com/nodatime/nodatime/issues/1834#issue-2655612378.