Worked on the LifeSG/react-design-system repository to deliver a calendar user experience enhancement focused on multi-date selection. Developed a multi-select variant for the Calendar component using React, JavaScript, and TypeScript, enabling users to select multiple dates while preserving backward compatibility for existing integrations. Introduced new components and updated internal logic to support the expanded selection model, and implemented a clear deprecation path with warnings to minimize migration risk. Comprehensive tests were written to cover selection, deselection, and controlled state scenarios, while documentation and stories were expanded to facilitate adoption and reduce onboarding friction for other developers and teams.