We require an expert freelancer to develop a robust customized calendar application for managing reservations across multiple vacation rental properties. The calendar needs to allow owners to view availability and bookings concurrently across all listings in an intuitive interface. This is an ongoing long-term engagement to create a sophisticated vacation rental management program with functionalities like centralized reservation handling, payment processing, channel manager integration and analytics. The ideal candidate will have extensive experience creating complex custom calendar solutions in HTML as well as a proven history of successful ongoing engagements with clients. Proficiency in full-stack development is preferred as the program will require integrating multiple features into a cohesive whole.