KAFKA-18400: Don't use YYYY when formatting/parsing dates in Java client

[kirktrue]

Changing documented date format to be ISO 8601 vs. SimpleDateFormat.

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[kirktrue]

Needs unit tests.

[AndrewJSchofield]

Thanks for the PR. I understand the distinction between year and week year, and it is certainly the case that the formatting and parsing should be using year (yyyy) and not week-year (YYYY). However, I feel the change of capitalisation of the format examples in the help messages is unhelpful to actual humans. If you want to be really pedantic about the use of SimpleDateFormat, the seconds and milliseconds should be ss.SSS, not SS.sss. However, in the help string, it's pretty clear what is meant.

[AndrewJSchofield]

Since you are correcting YYYY to yyyy, you should also correct SS.sss to ss.SSS since "s" is seconds and "S" is milliseconds for SimpleDateFormat.

[kirktrue]

The format that is used to parse the user-supplied timestamp is ISO 8601-based. The question is: Should we present to the user the date format in terms of the ISO spec or that of SimpleDateFormat? I don't want to bikeshed this PR, but my preference is to keep the internals separate from the user-facing documentation.

[AndrewJSchofield]

The format that is used to parse the user-supplied timestamp is ISO 8601-based. The question is: Should we present to the user the date format in terms of the ISO spec or that of SimpleDateFormat? I don't want to bikeshed this PR, but my preference is to keep the internals separate from the user-facing documentation.

I agree. I think what you've done here is appropriate.