Abstract: System, method, and computer program and computer program product for change analytics based forecast and query optimization and impact identification in a variance-based forecasting system with visualization. Server side system and method and client side customer system and method and interface. Variance engine and processor and processing method. Systems and methods for generating, displaying, and interacting with future event forecasts, and more particularly to systems, methods, computer programs, and applications for a delta, change, or variance based forecast interaction and visualization with event impact assessment and method for query optimization and impact identification in a variance based forecasting system and method.