chrono::MAX_DATETIME is not deserializable via parse_from_rfc3339

[Veetaha]

Steps to Reproduce

Run the following code (playground)

use std::str::FromStr;
use chrono::{DateTime, Utc};

fn main() {
    let max_dt = chrono::MAX_DATETIME;
    
    let str = max_dt.to_rfc3339();
   
    // This works fine though
    assert_eq!(max_dt, DateTime::<Utc>::from_str(&str).unwrap());
    
    // But this panics on `unwrap`
    assert_eq!(max_dt, DateTime::parse_from_rfc3339(&str).unwrap());
}

Context

Our code creates a timestamp with the maximum value to represent a record that never expires and it fails at deserialization. We are going to use regular from_str to workaround the problem, but still I'd expect DateTime::parse_from_rfc3339(dt.to_rfc3339())) to be purely an identity conversion. Is it a bug or is it intended?

Offtopic Context

I am using RFC3339 representation to store the timestamp in a DynamoDB database string property to have it lexicographically sortable. As I see all values after 9999 year have a plus sign and a variable amount of digits in the year. Unfortunately, it messes up the monotonic nature of this format =(. I guess we will have to just accept that we can't have timestamps properly sorted for years more than 9999 just because we will never have such values during our lifespan. Do you have any suggestions for a better solution for this particular problem?

[djc]

I think this is a bug in the to_rfc3339() implementation: anything that's not a 4-digit year does not appear to be a valid RFC date. Problem would be that changing to_rfc3339() to be fallible would cause the API to be incompatible. Something to think about...

[pitdicker]

So the issue is that RFC 3339 doesn't support dates beyond 0..=9999.

I opened #1144 to replace to_rfc3339() with to_iso8601 (which does support arbitrary years if preceded by a sign) and a fallible try_to_rfc3339