No. It is a literal 24 hr. day.
That's the most probable opinion, but the Pontifical Biblical Commission under St. Pius X permitted entertaining a metaphorical interpretation of a day which was not 24 hours.
People have to understand that this is not a license to treat the Book of Genesis as anything other than a historical text, but it's simply a metaphorical use of a single word, the term "day", in an extremely limited way.
Since the Pontifical Biblical Commission under St. Pius X permitted this, Hahn is not wrong that Catholics are permitted to hold that the days of Genesis were not 24-hour days.
This is coming from someone (myself) who holds that Father Robinson's interpretations of Scripture are heretical, that it's heretical to claim that people have been on earth for longer than about 6,000 +/- years, and a very serious error (proximate to heresy) to reject the existence of a solid / physical firmament that keeps literal physical waters off the earth from above the firmament. So I'm not a laxist regarding the loose interpretation of Sacred Scripture, but the use of a word like day in a metaphorical sense I don't consider to be in the same category, and neither did the Pontifical Biblical Commission.