The early Christians...Barnabus in this example understood the days to be 24 hour long period of times. Keep in mind this text is extra biblical and not to be taken as inspired...but it does show their belief in a literal six day creation. If the days were "eons" then what Barnabus wrote wouldn't work.
15:2 And in another place he saith, If my sons shall
keep my sabbath, then will I place my mercy upon them.
15:3 He speaketh, too, of the sabbath in the
beginning of the creation: And God made in six days
the works of his hands, and finished them on the
seventh day, and rested in it and sanctified it.
15:4 Consider, my children, what signify the words,
He finished them in six days. They mean this: that in
six thousand years the Lord will make an end of all
things, for a day is with him as a thousand years. And
he himself beareth witness unto me, saying: Behold
this day a day shall be as a thousand years.
Therefore, my children, in six days, that is in six
thousand years, shall all things be brought to an end.
15:5 And the words, He rested on the seventh day,
signify this: After that his Son hath come, and hath
caused to cease the time of the wicked one, and hath
judged the ungodly, and changed the sun and the moon
and the stars, then shall he rest well on the seventh
day.