Young Earth Creationists (YECs) do not dispute this—but they argue that every time yom is used in an ordinal sense: first day, second day, etc., it refers to a literal day. There are, YECs claim, no exceptions.
For example, in this AiG post, point 3.a.i, uber-YEC Ken Ham, writes, "Yom + ordinal number (used 410 times) always indicates an ordinary day [i.e. a 24-hour period]."
Even if Ham and other YECs are correct, that all instances of yom with an ordinal number outside of Genesis 1 refer to 24-hour days, it does not prove that the use of yom with ordinal numbers in Genesis 1 must refer to 24-hour days. Perhaps it is just more likely to have occasion to use first day, second day, etc. than first age, second age. The use in Genesis is then a rarely needed construction rather than a violation of ancient Hebrew grammar. It is simply more likely that we should discuss a sequence of days rather than ages—indeed Genesis 1 may be the only place where, even potentially, an ordinal sequence of ages appears. I can’t think of another in the Old Testament.
In places where it is conceded that yom is indeterminate—such as in the "day of the Lord"—the passages are speaking only of one yom of the Lord. We wouldn’t expect them to read “The first day of the Lord” or “The first and only day of the Lord.”
Nevertheless, if I were a YEC, I’d probably bring up the “ordinal” usage argument, not as proof but as evidence.
Which brings me to to my point.
In Hosea, we read:
1“Come, let us return to the LORD;In verse 2, the word yom (day) is used with an ordinal number—the third day. Yet the common interpretation of this passage is both as a Messianic prophesy and the expectation of a long, indeterminate period of affliction and suffering for Israel (e.g., see the commentaries by John Calvin and Matthew Henry).
for he has torn us, that he may heal us;
he has struck us down, and he will bind us up.
2 After two days he will revive us;
on the third day he will raise us up,
that we may live before him. (Hosea 6:1-2)
So how do YECs reconcile this? I am sure they do, but I cannot find it. I hope someone can provide some additional information.
In addition to information on how YECs explain Hosea 6:2, I have another question for YECs and Hebrew scholars: if the Old Testament did have need to describe an ordinal sequence of ages, what word would it use in place of yom? I'm not asking because I don't think there is an answer. I'm asking because I don't know the answer.