As far as I remember as a jw ,each creative day was a 1000 year, so 6000 years took us to 1975.
And then because of advances in understanding the age of the earth etc it was changed to each day being a undisclosed period of time.
The bible is not a scientific book, it's a book of fiction and mythology. So why anyone would believe that it is to be taken literally in the 21st century is beyond sensibility and to ignore and dismiss the overwhelming evidence for the age of the earth etc.