Floor pre-epoch Timestamp seconds in DateTimeConverter.convertToType

[rootvector2]

DateTimeConverter.convertToType decomposes a java.sql.Timestamp into whole seconds with timestamp.getTime() / 1000 * 1000 and adds the sub-second part back via timestamp.getNanos() / 1000000, but integer division truncates toward zero while getNanos() is always in [0, 999999999] (the JDK constructor borrows a second to normalize a negative fraction), so a pre-epoch timestamp with a non-zero fraction rounds the whole-second term up toward zero and then adds a non-negative nanos term, gaining a full second: new java.sql.Timestamp(-500L) (1969-12-31T23:59:59.500Z) converts to epoch millis 500 instead of -500. Math.floorDiv makes the whole-second term floor so it agrees with the nanos term; every date/time converter inherits this one path and post-epoch values are unchanged. Found auditing the date/time converters; the existing tests only feed positive System.currentTimeMillis(), so they never hit it.

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[Copilot]

Pull request overview

This PR fixes DateTimeConverter.convertToType for pre-epoch java.sql.Timestamp values with a fractional component by using floor semantics when deriving the whole-second millisecond portion, and adds a regression test to cover the negative timestamp case.

Changes:

• Use Math.floorDiv when deriving whole-second milliseconds for java.sql.Timestamp conversions to avoid rounding toward zero for negative timestamps.
• Add a unit test that verifies converting new Timestamp(-500L) preserves -500 epoch millis.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/main/java/org/apache/commons/beanutils2/converters/DateTimeConverter.java	Adjusts timestamp whole-second computation to floor for negative values.
src/test/java/org/apache/commons/beanutils2/converters/DateConverterTest.java	Adds a regression test for pre-epoch Timestamp conversion correctness.

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[garydgregory]

Hello @rootvector2
Please review Copiolot's comment. The comment suggests we are also missing a unit tests for the path Copilot found. Please verify and provide an additional test.
Thank you!