After successfully defending my PhD thesis in October 2019, the panel chair sternly warned me. First, I was forbidden from referring to myself as a "Dr" until I graduated in a ceremony that would be held in December of the same year.
Second, when we went for the graduation ceremony rehearsal a day before D-day, we were given strict instructions not to put on the doctoral tam (a graduation cap worn with a gown and hood) but await the university chancellor, and the accompanying authorities do so while reading the citation to admit us into the doctorate 'club' on the graduation day.