On Michaelmas day, which that year (1506) came on Tuesday, September 29th, he read his first mass in the parish church at Wildhaus. He then went to Glarus.
Or more fully, according to West
At ten years of age Zwingli was sent to Basel to study and then to Bern and Vienna (at around fifteen years of age) where he earned a Bachelor’s degree. By 1506 he had earned a Master of Arts at Basel’s famous University and then shortly after celebrated his first Mass at his hometown before moving to Glarus to take up his priestly office. It was while he was in that picturesque village that Zwingli poured himself into his studies of the Bible, led by the urgings of Erasmus, who was then the leader of learning in Switzerland and across western Europe. According to his own testimony, it was in 1515 that the ‘reformatory’ spirit began to stir in his heart so that when he moved to Einsiedeln (in 1516) to serve the congregation there, he was already pursuing the beginnings of Reformed thought.
Happy First Mass Day, Huldrych, and thank Heaven that you left that superstition behind by 1520.