Since it SAYS 24 hour period, it's the same day we know as a day.
The word used for day ONLY means a 24 hour day.
God doesn't mince words.
It does not in anyway specify 24, much less 24 hours.
By the way, since you are relying upon the infallibility of human language, perhaps you'd like to compare the use of any number of words which have changed conotation in the last 50 years just in the U.S., much less the changes between the time the King James Bible was translated, and now.
There are several other layers of things you are overlooking in making such a brash claim.
And just because you will probably come to this sooner or later: I believe that God created the Heavens and Earth. I just think you undermine your own case with your claims.