Sebastien Leveque enhanced time formatting capabilities in the symfony/console and symfony/symfony repositories by introducing millisecond precision to the formatTime function. Working primarily in PHP, he focused on backend development and unit testing to ensure accurate and consistent duration representations in CLI outputs and logs. Sebastien updated and expanded test coverage to validate millisecond-level accuracy, aligning the behavior of the console component and the broader framework. This work addressed the need for more granular time measurements in analytics and debugging workflows, laying the foundation for improved reliability and developer experience across projects that rely on precise time tracking in PHP applications.