Even now the length of a day changes. If the theories of solar system creation are anything close to valid, then the length of a day on Earth has changed dramatically over the course of its lifetime.
True, Fardels! An Earth day was originally much shorter; when the Earth first coalesced / condensed out of the nebula, it might have been approx. 12 hours long. But now YOU are equivocating, Fardels. A mere 50% shorter day is hardly "dramatic" in the context of cosmology.
For BereanBrain's statement to have any REAL validity, an Earth day would have had to originally have been thousands or millions of years in length. Only then could, e.g., animal life have "come forth" in a single day, as a LITERAL reading of Genesis claims!
Regards,