The May 1, 2013, edition of the Ames Sentinel arrived in June.
The Ames Sentinel—dated May 1, 2013—arrived in June.
Could you explain to me the presence of the definite article in the first sentence ("The May"). I was thought the rule that the zero article is used when the number in function of adjective comes after the noun, e.g. World War 2 or page 25.