Despite the multiple efforts to understand the temporal evolution of the Ecuadorian Volcanic Arc, the evolutionary history of the oldest volcanic edifices remained poorly studied. The Paris-Saclay University, the Instituto Geofísico of the Escuela Politécnica Nacional and the French Instituto de Investigación para el Desarrollo carried out an ambitious research project where more than 140 K-Ar dates were obtained for more than 30 volcanoes of the arc. These high quality ages showed that most of the volcanoes are younger than previously thought, with formation ages of less than 600 ka. This contribution summarizes the K-Ar dating technique employed, the sampling strategies and laboratory processes that ensure the quality of the results, as well as our key geochronological findings of the last decade.