The precise date of the Council of Serdica is so important because it is essential for establishing the chronology of numerous events in fourth-century Christianity, and thus for reconstructing its overall history and developments. Unfortunately, this date has been under debate for nearly two centuries. Traditionally, the council was dated to 347 C.E., but discoveries in the 18 th and 19 th centuries led scholars to favor first 344 and then 343. In the early 20 th century, Eduard Schwartz inaugurated a new stage in the debate when he argued for 342. In his wake, most French, Italian, and English-speaking scholars argued for 343, whereas most German-speaking scholars followed Schwartz's authority and endorsed 342. In 1974, Marcel Richard advanced a novel argument in favor in 342 that appeared to cement this date for its advocates. Recently, however, 343 appears to be the preferred date even in German scholarship. After more than a century of debate, it seems, a consensus has been reached. This essay offers the most comprehensive reassessment of this debate to date to see if it really should be considered concluded. It re-examines all the evidence and all the arguments made in support of one date or another, in particular those of Schwartz and Richard, and argues that the case for the Council of Serdica's having been held in the autumn of 343 should be considered conclusive; thus, the lengthy debate can rightly be closed.