Here's the thing, the Hebrew word for day, is 'yom' and it has been argued that a day, is not necessarily a 24 hour period, because of phrases such as 'back in the day' meaning a period of time, or 'in the day of the dinosaurs' because we know they had more than a day.
But the problem with that usage, is that Genesis numbers the days. The days are discrete entities, not a continuum. The days also have mornings and evenings. Clearly, we are not talking about a vague 'back in the day' use of the word.
So trying to say 'yom' wasn't what we understand to be a 24 hour day, is yet more apologetics.
Except that Hebrew treats the words for morning and evening with the same ambiguity, such as in "dawn of a new day". The link I provided earlier gives many examples of this.