Support lenient parsing for dates using AM/PM in conjunction with `@DateTimeFormat`

[sbrannen]

Overview

This is a follow-up to #30185 and #33151.

When applications run on JDK 23+, Spring Framework should support lenient parsing for date/time formats that include the time period (AM or PM) -- for example, by matching leniently against a narrow non-breaking space (NNBSP) or a standard space between the hour and AM/PM declaration.

Related Resources

• https://jdk.java.net/20/release-notes#JDK-8284840
• https://unicode-org.atlassian.net/browse/CLDR-14032
• https://bugs.openjdk.org/browse/JDK-8223587
• https://bugs.openjdk.org/browse/JDK-8284840
• https://bugs.openjdk.org/browse/JDK-8297316
• https://bugs.openjdk.org/browse/JDK-8304925
• https://bugs.openjdk.org/browse/JDK-8324665

Related Issues

• Ensure compatibility with JDK 20 #30185
• Adapt Date/Time formatting tests to accommodate narrow non-breaking spaces #33144
• Document options for handling Date/Time parsing and formatting issues with JDK 20+ #33151

[sormuras]

"Loose matching of space separators in the lenient date/time parsing mode" has been integrated into Java 23-ea+9:

• openjdk/jdk@96eb039

See JDK-8324665 for more details.

[snicoll]

We should move this to 6.1.x otherwise we can't build against Java 23. It's unfortunate we've been hiding this problem for so long. COMPAT is now deprecated and we should stop using it ASAP.