Fix RFC 850 two-digit year parsing

[medz]

Summary

• resolve RFC 850 two-digit years relative to the current UTC year
• apply RFC 9110's 50-year rollover rule
• add a regression test for the reported 2026 date
• update the API documentation and changelog

Root cause

parseHttpDate() always added 1900 to RFC 850's two-digit year, so 26 was parsed as 1926 regardless of the current year.

Impact

RFC 850 timestamps such as those used in Retry-After headers now resolve to the correct century instead of potentially being treated as expired.

Closes #1939

Validation

• dart format --output=none --set-exit-if-changed .
• dart analyze --fatal-infos
• dart test --platform vm
• dart test --platform chrome
• dart test --platform chrome --compiler dart2wasm

[github-actions]

PR Health

Unused Dependencies ✔️

Package	Status
http_parser	✔️ All dependencies utilized correctly.

For details on how to fix these, see dependency_validator.

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Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
http_parser	None	4.1.2	4.1.3-wip	4.1.3-wip	✔️

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API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

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Changelog Entry ✔️

Package	Changed Files

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Coverage ✔️

File	Coverage
pkgs/http_parser/lib/src/http_date.dart	💚 100 %

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License Headers ✔️

// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

Files
no missing headers

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Unrelated files missing license headers

Files
pkgs/cupertino_http/example/example.dart
pkgs/http/example/main.dart
pkgs/http_multi_server/test/cert.dart

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[brianquinlan]

Could you fix the lint so that I can merge this?

[medz]

Could you fix the lint so that I can merge this?

fixed