Some vegans first suggested celebrating in September. The second day of September was the birthday of Donald Watson, who put together the first copy of The Vegan News. But Donald said the day shouldn’t be focused on a person; so vegans chose the opening day of November—marking the anniversary of that first issue.
One more thing: Not only did Donald Watson eschew the famous-person mantle, but Donald actually did not take credit (sorry, Wikipedia) for coining the word vegan…