Worked on the apache/datafusion-comet repository to resolve a critical issue in date-time processing, specifically addressing ambiguities and non-existent local times during daylight saving transitions. Using Rust and Scala, implemented logic to consistently select the earliest valid local time when ambiguity arises and to handle non-existent times correctly. Enhanced reliability by refactoring unit tests, removing unstable constructs, and adding comprehensive coverage for edge cases involving DST casting with Spark. The work focused on improving code clarity and robustness, ensuring that date-time operations behave predictably across complex scenarios. This contribution strengthened the reliability of time-related features without introducing new user-facing features.