Well. yes---
The day starts in the evening, and ends at the end of the morning. So, yes, It's 12 hrs, evening, 12 hour morning, 24 hr.
There are 24 verses with evening and morning mentioned. From Gen to Acts. Those obviously mean 12 hr---they say--from evening unto the morning, or from morning to evening, or morning till evening. Dan. 8 I believe seems to indicate the same thing--
The difference with Gen. 1 is that the days are numbered, Day one to day 7. The evening and the morning, day one. The evening and the morning day two--and so on. There really can be no other interpretation but 24 hr days. Evening and morning--one eon? The vegetation was all on day 3---then the sun on the 4th day. To read that as though it was an eon when the vegetation was without sun, makes no sense whatsoever. That the sun was created the next day--so they didn't have the sun for several hrs, no big deal, they won't die, there was still the invisible light from day one till then. And again, to then say that after He had created man He rested from creating for an eon and hallowed and sanctified an eon makes no sense either.
Gen 2:3 And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.
And you csn not then read Exodus as eons either.
Exo 20:11 For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it.
He did not instruct the Jews to not work for eons---He says He created the world in 6 days there, and He wrote it with His own finger twice. He ceased work on the 7th day and He sanctified that day, not that age.