Reflective solar band (RSB) calibration of the Visible Infrared Imaging Radiometer Sensor Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) satellite was automated in November 2015. The algorithm and science code for automating RSB calibration, known as RSBAutoCal, were developed by The Aerospace Corporation as part of its support to the VIIRS calibration/validation (cal/val) effort led by the NOAA Center for Satellite Applications and Research (STAR). Prior to its automation, RSB calibration was performed via weekly updates of look-up tables (LUTs) ingested by the Sensor Data Record (SDR) ground processing performed by the Interface Data Processing Segment (IDPS). RSBAutoCal has significantly improved the accuracy and stability of the VIIRS RSB calibration relative to the prior LUT based approach. In this paper we quantify this improvement based on a full year of calibration data, showing that RSBAutoCal is essential to reduce predict-ahead error, one component of accuracy, below 0.1%.