This document presents a new phenology model called the Grapevine Flowering Veraison Model (GFV) to characterize the timing of flowering and ripening (veraison) of Vitis vinifera L. The GFV was tested on over 4,000 phenology observations across Europe and performed better than existing models. It uses a simple thermal time summation approach starting on March 1st with a base temperature of 0°C. The GFV provides an easy to use and accurate tool for predicting grapevine development timing and classifying varieties by precocity.