The presentation was given as part of the CESSDA Training Days. The CESSDA Training Days were a two-day training event showcasing diverse training resources on both CESSDA tools and services. They took place on November 27 and 28, 2019, and were hosted by the GESIS – Leibniz-Institute for the Social Sciences in Cologne, Germany. All courses were held in English. The Training Days were supported by CESSDA Training, and were the first of what is to become a series of annual training events. Katharina Blinzler introduced definitions and strategies of data harmonization, and demonstrated which measures an international and multicultural survey project, the Comparative Study of Electoral Systems (CSES) applies throughout its survey lifecycle to enhance data comparability across countries.