So I heard that a "Day" is actually translated "period [of time]"

I don't think that heavenly version of a day vs earthly would be relevant (no offense), because God would have relayed the information to us using the terms we understand. If He says "morning" and "evening" and "day", I don't think he'd be trying to fool anyone. He could have just as easily indicated that it was a "time" if He wanted to be vague. Previous forum posters have shown that the Hebrew doesn't indicate any odd usage of the word, so I think we're stuck with approximately 24 hr days (if anything, they would have been slightly shorter previously, since the earth's rotation is gradually slowing due to transference of energy to the moon).