Well, according to Wiki there's no simple answer. National Allied Publications, the precursor to DC Comics along with Detective Comics Inc., published it's first titolo in February 1935. National and Detective merged in 1944 to form National Comics, but had already been printing Detective Comics and Action Comics. National Comics was the official name of the line until they officially adopted DC Comics which they had been using unofficially for some time. But Wiki doesn't say when the change was made. So if we wanna get technical, this mese is the 75th Anniversary since the original National Allied Publications originated Detective Comics.
