Any chance on getting this merged for .NET 9?

Any chance of getting this merged for 9.0.2?

This is very simple fix for a bug caused by a small typo. There is almost zero risk to merging this, and it would fix a bug that has existed in my application for a year now.

@dotnet-policy-service rerun

/azp run runtime

Thanks @dougwaldron! This is a solid improvement that brings our RSS date handling closer to the intent of RFC 822 while keeping the existing layered fallback behavior.

For anyone following along: the current RSS date parsing path (see the internal helper in System.ServiceModel.Syndication) tries, in order:

1. A straight DateTimeOffset.TryParse(...) on the raw string (to catch many already-well‑formed or framework-supported variants)
2. An RFC 822–style parse (normalizing the time zone token before parsing)
3. An RFC 3339 (Atom-style) parse as a pragmatic fallback (since feeds in the wild often mix styles)

That balance lets us stay compliant yet resilient. This PR tightens conformance in the RFC 822 layer without removing the practical fallbacks.

Reminder: If you encounter feeds whose date strings are even more “creative” (e.g., ordinal day tokens, missing commas, non-English month names, 2‑digit years, or embedded comments), you do NOT have to push further loosening into the core library. You can plug in your own parsing logic via the public delegate hook:

using System;
using System.ServiceModel.Syndication;

// Do this once early in app startup (before loading feeds).
// Capture the existing parser so you can chain/fallback.
var originalRssParser = Rss20FeedFormatter.DateTimeParser;

// Install a custom parser
Rss20FeedFormatter.DateTimeParser = (xmlDateTimeData, out DateTimeOffset dto) =>
{
    // xmlDateTimeData.DateTimeString is the raw value.
    // Return true if you successfully parsed; set dto accordingly.

    if (MyVeryForgivingParser(xmlDateTimeData.DateTimeString, out dto))
    {
        return true;
    }

    // Fall back to the framework’s (now improved) default behavior
    return originalRssParser(xmlDateTimeData, out dto);
};

// Example custom routine (simplified)
static bool MyVeryForgivingParser(string s, out DateTimeOffset dto)
{
    // Your heuristics here (strip ordinal suffixes, normalize TZ tokens, etc.)
    // Return true on success.
    dto = default;
    return false;
}

(Atom feeds have an analogous hook via Atom10FeedFormatter.DateTimeParser.)

A few tips when customizing:

• Keep your parser narrowly scoped: only handle the truly outlier patterns you see.
• Chain to the original so you inherit spec-aligned improvements like the one in this PR.
• If you need per-feed experimentation, you can temporarily swap the delegate, parse, then restore it—but prefer a stable global install to avoid races.

Given the clear standards improvement and low risk, I’m proceeding with the merge. Thanks again for tightening this up and helping the ecosystem stay closer to the spec while still allowing extensibility.

/backport to release/10.0

Started backporting to release/10.0: https://github.com/dotnet/runtime/actions/runs/17871053134